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Inverse element

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5493: 4930: 5488:{\displaystyle {\begin{aligned}AA^{\text{T}}&={\begin{bmatrix}1&2&3\\4&5&6\end{bmatrix}}{\begin{bmatrix}1&4\\2&5\\3&6\end{bmatrix}}={\begin{bmatrix}14&32\\32&77\end{bmatrix}}\\\left(AA^{\text{T}}\right)^{-1}&={\begin{bmatrix}14&32\\32&77\end{bmatrix}}^{-1}={\frac {1}{54}}{\begin{bmatrix}77&-32\\-32&14\end{bmatrix}}\\A^{\text{T}}\left(AA^{\text{T}}\right)^{-1}&={\frac {1}{54}}{\begin{bmatrix}1&4\\2&5\\3&6\end{bmatrix}}{\begin{bmatrix}77&-32\\-32&14\end{bmatrix}}={\frac {1}{18}}{\begin{bmatrix}-17&8\\-2&2\\13&-4\end{bmatrix}}=A_{\text{right}}^{-1}\end{aligned}}} 5692: 3903:
have an inverse as defined in this section. Under this more general definition, inverses need not be unique (or exist) in an arbitrary semigroup or monoid. If all elements are regular, then the semigroup (or monoid) is called regular, and every element has at least one inverse. If every element has
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A matrix has a left inverse if and only if its rank equals its number of columns. This left inverse is not unique except for square matrices where the left inverse equal the inverse matrix. Similarly, a right inverse exists if and only if the rank equals the number of rows; it is not unique in the
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The definition in the previous section generalizes the notion of inverse in group relative to the notion of identity. It's also possible, albeit less obvious, to generalize the notion of an inverse by dropping the identity element but keeping associativity; that is, in a
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is a field, the determinant is invertible if and only if it is not zero. As the case of fields is more common, one see often invertible matrices defined as matrices with a nonzero determinant, but this is incorrect over rings.
5687:{\displaystyle A^{\text{T}}A={\begin{bmatrix}1&4\\2&5\\3&6\end{bmatrix}}{\begin{bmatrix}1&2&3\\4&5&6\end{bmatrix}}={\begin{bmatrix}17&22&27\\22&29&36\\27&36&45\end{bmatrix}}} 4922: 1854:
Given a monoid, one may want extend it by adding inverse to some elements. This is generally impossible for non-commutative monoids, but, in a commutative monoid, it is possible to add inverses to the elements that have the
3919:. This is generally justified because in most applications (for example, all examples in this article) associativity holds, which makes this notion a generalization of the left/right inverse relative to an identity (see 4935: 1062: 4734: 2782:. An invertible homomorphism or morphism is called an isomorphism. An homomorphism of algebraic structures is an isomorphism if and only if it is a bijection. The inverse of a bijection is called an 2757: 631: 4515: 4362: 2557: 1276: 2648: 4520: 4367: 489: 308: 279: 4742:
matrix has any (even one-sided) inverse. However, the Moore–Penrose inverse exists for all matrices, and coincides with the left or right (or true) inverse when it exists.
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In a monoid, the notion of inverse as defined in the previous section is strictly narrower than the definition given in this section. Only elements in the Green class
2614: 2940: 2583: 1426: 749: 2145: 1356: 3969:, this is not necessarily the case. In order to obtain interesting notion(s), the unary operation must somehow interact with the semigroup operation. Two classes of 2908: 1701: 864: 3435: 3337: 3235: 2972: 1954: 1893: 4654: 3657: 1922: 1018: 708: 3880:. An intuitive description of this fact is that every pair of mutually inverse elements produces a local left identity, and respectively, a local right identity. 1981: 1557: 1531: 1319: 786: 679: 1767: 1744: 989: 413: 4307: 4283: 4253: 4225: 4202: 3628: 3592: 3192: 3168: 3148: 3120: 3100: 3080: 3060: 3036: 3016: 2992: 2879: 2848: 2704: 2672: 1721: 549: 4751: 1775:
represents the finite sequences of elementary moves. The inverse of such a sequence is obtained by applying the inverse of each move in the reverse order.
2422:(that is, matrices with integer entries), an invertible matrix is a matrix that has an inverse that is also an integer matrix. Such a matrix is called a 897:
Left and right inverses do not always exist, even when the operation is total and associative. For example, addition is a total associative operation on
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is zero, it is impossible for it to have a one-sided inverse; therefore a left inverse or right inverse implies the existence of the other one. See
3602:(an associative unital magma) every element has at most one inverse (as defined in this section). In a monoid, the set of invertible elements is a 1828:, there may exist non-invertible elements that have a left inverse or a right inverse (not both, as, otherwise, the element would be invertible). 924:
An element can have several left inverses and several right inverses, even when the operation is total and associative. For example, consider the
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for which one of the members of the equality is defined; the equality means that the other member of the equality must also be defined.
4110:. Since *-regular semigroups generalize inverse semigroups, the unique element defined this way in a *-regular semigroup is called the 964:, which are the functions that divide by two the even numbers, and give any value to odd numbers. Similarly, every function that maps 4667: 1023: 1392:
When there may be a confusion between several operations, the symbol of the operation may be added before the exponent, such as in
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In the common case where the operation is associative, the left and right inverse of an element are equal and unique. Indeed, if
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has both a left inverse and a right inverse, then these two inverses are equal and unique; they are called the
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A natural generalization of the inverse semigroup is to define an (arbitrary) unary operation ° such that (
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over a ring: a homomorphism of modules that has a left inverse of a right inverse is called respectively a
1670: 1168: 1204: 4617:{\displaystyle A\underbrace {A^{\text{T}}\left(AA^{\text{T}}\right)^{-1}} _{A_{\text{right}}^{-1}}=I_{m}} 4055: 3237:
may have multiple left, right or two-sided inverses. For example, in the magma given by the Cayley table
20: 4464:{\displaystyle \underbrace {\left(A^{\text{T}}A\right)^{-1}A^{\text{T}}} _{A_{\text{left}}^{-1}}A=I_{n}} 5889: 3444:
Similarly, a loop need not have two-sided inverses. For example, in the loop given by the Cayley table
3908:. Finally, an inverse semigroup with only one idempotent is a group. An inverse semigroup may have an 2522: 5884: 4063: 3998: 3598:
then if an element has both a left inverse and a right inverse, they are equal. In other words, in a
1164: 432: 284: 255: 215:. They are also commonly used for operations that are not defined for all possible operands, such as 2490: 4015: 2768: 1659: 1562: 1102: 5789:"MIT Professor Gilbert Strang Linear Algebra Lecture #33 – Left and Right Inverses; Pseudoinverse" 4173:
and one uniquely determines the other. They are not left or right inverses of each other however.
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with a type ⟨2,1⟩ algebra. A semigroup endowed with such an operation is called a
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Outside semigroup theory, a unique inverse as defined in this section is sometimes called a
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case of a rectangular matrix, and equals the inverse matrix in the case of a square matrix.
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is a monoid for ring multiplication. In this case, the invertible elements are also called
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that are everywhere defined (that is, the operation is defined for any two elements of its
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that means 'turned upside down', 'overturned'. This may take its origin from the case of
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is an invertible element under matrix multiplication. A matrix over a commutative ring
2276: 2245: 2103: 2030: 2006: 1986: 1844: 1840: 1825: 1814: 1810: 1706: 823:, and the composition of the identity functions of two different sets are not defined. 534: 212: 208: 197: 189: 181: 4822:{\displaystyle A:2\times 3={\begin{bmatrix}1&2&3\\4&5&6\end{bmatrix}}} 4030:-semigroup and a *-semigroup. A class of semigroups important in semigroup theory are 5830: 5810: 5753: 5745: 4256: 4146: 3909: 3905: 3818:. Thus, every pair of (mutually) inverse elements gives rise to two idempotents, and 3675: 2855: 2810: 2772: 2764: 2454: 2423: 2380: 2061: 1640: 906: 816: 552: 385: 377:
must be extended to partial operations; this is the object of the first subsections.
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The usual definition of an identity element has been generalized for including the
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exactly one inverse as defined in this section, then the semigroup is called an
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of the localisation; instead, it is mapped non-injectively to the localization.
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have an inverse from the unital magma perspective, whereas for any idempotent
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defines a transformation that is the inverse of the transformation defined by
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Monoids, Acts and Categories with Applications to Wreath Products and Graphs
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that has an identity element, and for which every element has an inverse.
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It follows that a total operation has at most one identity element, and if
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contains all of the semigroup material herein except *-regular semigroups.
5809:, De Gruyter Expositions in Mathematics vol. 29, Walter de Gruyter, 2000, 2430:. A square integer matrix is unimodular if and only if its determinant is 353:, that is operations that are not defined everywhere. Common examples are 4232: 4227:
is invertible (in the set of all square matrices of the same size, under
3595: 2481: 2427: 2300: 2057: 2053: 1624: 1612: 1359: 423: 314: 228: 157: 27: 4054:°. There are few concrete examples of such semigroups however; most are 1989:
construction. This is the method that is commonly used for constructing
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that is, the transformation that "undoes" the transformation defined by
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from the group to itself that may also be considered as an operation of
2798: 1153: 172:. Often an adjective is added for specifying the operation, such as in 2438:, since these two numbers are the only units in the ring of integers. 4627:
The left inverse can be used to determine the least norm solution of
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the only element with a two-sided inverse is the identity element 1.
2794: 2779: 2184: 1149: 5817:, p. 15 (def in unital magma) and p. 33 (def in semigroup) 2793:
A function has a left inverse or a right inverse if and only it is
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every element has a unique two-sided inverse (namely itself), but
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A unital magma in which all elements are invertible need not be a
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acts a right identity, and the left/right roles are reversed for
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for distinguishing it from matrices that are invertible over the
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under an operation if it has a left inverse and a right inverse.
917:. This lack of inverses is the main motivation for extending the 1057:{\textstyle n\mapsto \left\lfloor {\frac {n}{2}}\right\rfloor ,} 4729:{\displaystyle x=\left(A^{\text{T}}A\right)^{-1}A^{\text{T}}b.} 3599: 2817:. This terminology is also used for morphisms in any category. 2087: 1784: 2360:, that is, an identity element for matrix multiplication is a 1284:
of an invertible element is its unique left or right inverse.
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for which the left-hand sides of the equalities are defined.
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All examples in this section involve associative operators.
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In the function and homomorphism cases, this means that the
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If the operation is denoted as an addition, the inverse, or
4050:; in other words every element has commuting pseudoinverse 3774:
as defined in this section. Another easy to prove fact: if
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Nordahl, T.E., and H.E. Scheiblich, Regular * Semigroups,
2110:(for avoiding confusion with additive inverses) of a unit 5848:, Proc. Symp. on Regular Semigroups (DeKalb, 1979), 29–46 4070:* is not the pseudoinverse. Rather, the pseudoinverse of 3194:. An element with an inverse element only on one side is 2445: 2232:(that is, their product with a nonzero element cannot be 2045:, which are denoted as the usual operations on numbers. 2477:, and share many properties with function composition. 2364:(same number for rows and columns) whose entries of the 3300:
the elements 2 and 3 each have two two-sided inverses.
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are respectively a left inverse and a right inverse of
349:). However, these concepts are also commonly used with 5626: 5577: 5529: 5408: 5353: 5305: 5199: 5141: 5060: 5009: 4963: 4778: 2153: 1471: 1368: 1105: 1078: 1026: 289: 260: 16:
Generalization of additive and multiplicative inverses
5507: 4933: 4846: 4754: 4670: 4633: 4523: 4479: 4370: 4326: 4295: 4271: 4241: 4213: 4190: 3754:. Every regular element has at least one inverse: if 3636: 3616: 3580: 3411: 3313: 3211: 3180: 3156: 3136: 3108: 3088: 3068: 3048: 3024: 3004: 2980: 2948: 2916: 2890: 2867: 2836: 2726: 2692: 2660: 2622: 2591: 2565: 2525: 2493: 2120: 1963: 1930: 1901: 1869: 1752: 1729: 1709: 1679: 1565: 1539: 1513: 1434: 1398: 1331: 1301: 1207: 997: 974: 937: 837: 768: 716: 687: 661: 585: 537: 435: 398: 287: 258: 2752:{\displaystyle \operatorname {id} _{X}\colon X\to X} 2244:
from the ring of integers, and, more generally, the
4176: 3858:. This simple observation can be generalized using 328: 5686: 5487: 4916: 4821: 4728: 4648: 4616: 4509: 4463: 4356: 4301: 4277: 4247: 4219: 4196: 3651: 3622: 3586: 3429: 3331: 3229: 3186: 3162: 3142: 3114: 3094: 3074: 3054: 3030: 3010: 2986: 2966: 2934: 2902: 2873: 2842: 2751: 2698: 2666: 2642: 2608: 2577: 2551: 2511: 2387:is invertible if and only if its determinant is a 2275:, and straightforwardly extended to matrices over 2169: 2139: 1975: 1948: 1916: 1887: 1839:. In this monoid, the invertible elements are the 1761: 1738: 1715: 1695: 1597: 1551: 1525: 1484: 1453: 1420: 1384: 1350: 1313: 1270: 1152:, and it has a right inverse if and only if it is 1144:More generally, a function has a left inverse for 1129: 1091: 1056: 1012: 983: 952: 858: 780: 743: 710:(This results immediately from the definition, by 702: 673: 626:{\displaystyle x*e=x\quad {\text{and}}\quad e*y=y} 625: 543: 483: 407: 302: 273: 3866:in an arbitrary semigroup is a left identity for 515:Examples of non-total associative operations are 19:"Invertible" redirects here. For other uses, see 5871: 3437:is not a loop because the Cayley table is not a 2778:A function is invertible if and only if it is a 4058:. In contrast, a subclass of *-semigroups, the 1843:; the elements that have left inverses are the 113:. (An identity element is an element such that 4235:is different from zero. If the determinant of 3082:is both a left inverse and a right inverse of 2240:, which produces, in particular, the field of 321:, except when otherwise stated and in section 4145:The lower and upper adjoints in a (monotone) 2183:is never a unit, except when the ring is the 1847:, and those that have right inverses are the 4745:As an example of matrix inverses, consider: 3912:0 because 000 = 0, whereas a group may not. 2682:. In the morphism case, this means that the 2616:or, in the function and homomorphism cases, 2147:or, when the multiplication is commutative, 369:. It follows that the common definitions of 184:. In this case (associative operation), an 149:for which the left-hand sides are defined.) 4157:are quasi-inverses of each other; that is, 2202:if the multiplication is commutative, or a 211:—where invertible elements are also called 4038:-semigroups in which one additionally has 826: 3150:. An element with a two-sided inverse in 1985:This extension of a monoid is allowed by 5859:, 24(1), December 1982, pp. 173–187 5498:The left inverse doesn't exist, because 960:has infinitely many left inverses under 207:—where every element is invertible, and 188:is an element that has an inverse. In a 4262:More generally, a square matrix over a 2295:, because of the use of the concept of 1835:from a set to itself is a monoid under 1673:of this set. In this case, the inverse 928:from the integers to the integers. The 5872: 4510:{\displaystyle A:m\times n\mid m<n} 4357:{\displaystyle A:m\times n\mid m>n} 4066:. In this case however the involution 2446:Functions, homomorphisms and morphisms 2289:in this section, only matrices over a 870:is an identity element, one says that 5820: 4517:we have right inverses; for example, 4140: 4002:, in which the interaction axiom is ( 2473:into operations that are also called 4364:we have left inverses; for example, 3983:, in which the interaction axiom is 2825: 2198:is the only non-unit, the ring is a 1271:{\displaystyle l=l*(x*r)=(l*x)*r=r.} 655:are two identity elements such that 526: 322: 313:In this article, the operations are 5805:M. Kilp, U. Knauer, A.V. Mikhalev, 2786:. In the other cases, one talks of 1020:is a right inverse of the function 238:The word 'inverse' is derived from 13: 5846:Regular semigroups with involution 4014:°. Such an operation is called an 2820: 2086:Under multiplication, a ring is a 1559:is invertible, and its inverse is 14: 5901: 4316:have several one-sided inverses: 4289:its determinant is invertible in 4177:Generalized inverses of matrices 3669: 2219:infinite-dimensional vector space 2060:; it has an identity, called the 1863:has the cancellation property if 1163:, right inverses are also called 5823:Fundamentals of Semigroup Theory 4924:By components it is computed as 2552:{\displaystyle g\colon Y'\to Z,} 2480:In all the case, composition is 913:is the only element that has an 417: 329:Definitions and basic properties 5853:P-systems in regular semigroups 3973:-semigroups have been studied: 3926: 3762:then it is easy to verify that 2320:matrix (that is, a matrix with 2102:for multiplication is called a 2052:, which means that addition is 1167:, and left inverses are called 762:are different identities, then 607: 601: 555:associative operation on a set 484:{\displaystyle x*(y*z)=(x*y)*z} 303:{\displaystyle {\tfrac {y}{x}}} 274:{\displaystyle {\tfrac {x}{y}}} 223:. This has been generalized to 5781: 5772: 5763: 5738: 3646: 3640: 3424: 3412: 3326: 3314: 3224: 3212: 2743: 2540: 2512:{\displaystyle f\colon X\to Y} 2503: 1250: 1238: 1232: 1220: 1130:{\textstyle {\frac {n-1}{2}},} 1030: 941: 472: 460: 454: 442: 203:Inverses are commonly used in 1: 5799: 4032:completely regular semigroups 3700:if there exists some element 2674:equals or is included in the 2048:Under addition, a ring is an 1778: 1598:{\displaystyle y^{-1}x^{-1}.} 4121: 4056:completely simple semigroups 3961:. Although it may seem that 3307:. For example, in the magma 2643:{\displaystyle Y\subset Y'.} 2372:, and all other entries are 2356:, and only in this case. An 2170:{\textstyle {\frac {1}{x}}.} 1831:For example, the set of the 1630: 1454:{\displaystyle f^{\circ -1}} 1385:{\textstyle {\frac {1}{x}}.} 791:For example, in the case of 34:generalises the concepts of 7: 5704: 4840:, we have a right inverse, 4132: 4026:Clearly a group is both an 4018:, and typically denoted by 3846:acts as a left identity on 3205:Elements of a unital magma 2771:), which is called also an 2395:(that is, is invertible in 2259: 2072:has an inverse, called its 2024: 1485:{\textstyle {\frac {1}{f}}} 1174: 1092:{\textstyle {\frac {n}{2}}} 953:{\displaystyle x\mapsto 2x} 808:for every positive integer 227:, where, by definition, an 21:Invertible (disambiguation) 10: 5906: 5701:, and cannot be inverted. 4125: 3673: 2585:is defined if and only if 2236:). This is the process of 1321:Otherwise, the inverse of 819:are identity elements for 517:multiplication of matrices 312: 18: 5769:Howie, prop. 2.3.3, p. 51 5756:as identity elements for 5748:as identity elements for 3965:° will be the inverse of 2767:, algebraic structure or 2005:and, more generally, the 1461:is not commonly used for 341:are commonly defined for 5731: 3464: 3461: 3458: 3455: 3452: 3449: 3356: 3353: 3350: 3347: 3251: 3248: 3245: 3242: 2935:{\displaystyle a,b\in S} 2578:{\displaystyle g\circ f} 2267:is commonly defined for 1806:under monoid operation. 1421:{\displaystyle x^{*-1}.} 744:{\displaystyle e=e*f=f.} 5821:Howie, John M. (1995). 4312:Non-square matrices of 3873:and right identity for 2191:as its unique element. 2140:{\displaystyle x^{-1},} 2092:multiplicative identity 1650:Thus, the inverse is a 1351:{\displaystyle x^{-1},} 827:Left and right inverses 519:of arbitrary size, and 422:A partial operation is 5688: 5489: 4918: 4823: 4730: 4650: 4618: 4511: 4465: 4358: 4303: 4279: 4249: 4221: 4198: 4074:is the unique element 3730:is called (simply) an 3720:is sometimes called a 3653: 3624: 3588: 3431: 3333: 3231: 3188: 3164: 3144: 3116: 3096: 3076: 3056: 3032: 3012: 2988: 2968: 2936: 2904: 2903:{\displaystyle e\in S} 2875: 2844: 2775:in the function case. 2753: 2700: 2668: 2644: 2610: 2579: 2553: 2513: 2179:The additive identity 2171: 2141: 2108:multiplicative inverse 1977: 1950: 1918: 1889: 1763: 1740: 1717: 1697: 1696:{\displaystyle g^{-1}} 1599: 1553: 1527: 1494:multiplicative inverse 1486: 1455: 1422: 1386: 1352: 1315: 1272: 1131: 1093: 1058: 1014: 985: 954: 860: 859:{\displaystyle x*y=e,} 782: 745: 704: 675: 627: 545: 485: 409: 323:§ Generalizations 304: 275: 243: 178:multiplicative inverse 5758:matrix multiplication 5716:Latin square property 5689: 5490: 4919: 4824: 4731: 4651: 4619: 4512: 4466: 4359: 4304: 4280: 4250: 4231:) if and only if its 4229:matrix multiplication 4222: 4199: 4116:Moore–Penrose inverse 4064:Moore–Penrose inverse 3698:(von Neumann) regular 3654: 3625: 3589: 3432: 3430:{\displaystyle (S,*)} 3334: 3332:{\displaystyle (S,*)} 3232: 3230:{\displaystyle (S,*)} 3189: 3165: 3145: 3117: 3097: 3077: 3057: 3033: 3013: 2989: 2969: 2967:{\displaystyle a*b=e} 2937: 2905: 2876: 2845: 2754: 2701: 2669: 2645: 2611: 2580: 2554: 2514: 2403:can be computed with 2265:Matrix multiplication 2172: 2142: 2037:with two operations, 1978: 1951: 1949:{\displaystyle yx=zx} 1919: 1890: 1888:{\displaystyle xy=xz} 1857:cancellation property 1789:associative operation 1764: 1741: 1718: 1698: 1645:associative operation 1600: 1554: 1528: 1487: 1456: 1423: 1387: 1358:or, in the case of a 1353: 1325:is generally denoted 1316: 1273: 1148:if and only if it is 1132: 1094: 1059: 1015: 986: 955: 861: 793:matrix multiplication 783: 746: 705: 676: 628: 546: 486: 410: 355:matrix multiplication 305: 276: 5866:, 16(1978), 369–377. 5750:function composition 5505: 4931: 4844: 4752: 4668: 4656:, which is also the 4649:{\displaystyle Ax=b} 4631: 4521: 4477: 4368: 4324: 4293: 4269: 4239: 4211: 4188: 4128:Quasiregular element 4060:*-regular semigroups 3652:{\displaystyle U(S)} 3634: 3614: 3578: 3409: 3311: 3209: 3178: 3154: 3134: 3106: 3086: 3066: 3046: 3022: 3002: 2978: 2946: 2914: 2888: 2865: 2834: 2788:inverse isomorphisms 2724: 2690: 2658: 2620: 2609:{\displaystyle Y'=Y} 2589: 2563: 2523: 2491: 2463:algebraic structures 2457:that generalizes to 2399:. In this case, its 2342:matrix, the product 2151: 2118: 2068:; and every element 1961: 1928: 1917:{\displaystyle y=z,} 1899: 1867: 1849:surjective functions 1837:function composition 1750: 1727: 1707: 1677: 1563: 1537: 1511: 1507:are invertible, and 1492:can be used for the 1469: 1463:function composition 1432: 1396: 1366: 1329: 1299: 1205: 1146:function composition 1103: 1076: 1024: 1013:{\displaystyle 2n+1} 995: 972: 962:function composition 935: 899:nonnegative integers 835: 821:function composition 766: 714: 703:{\displaystyle e=f.} 685: 659: 583: 535: 521:function composition 433: 396: 359:function composition 285: 256: 30:, the concept of an 5480: 4864: 4598: 4442: 4112:generalized inverse 3921:Generalized inverse 3862:: every idempotent 2211:noncommutative ring 2100:invertible element 2035:algebraic structure 1976:{\displaystyle y=z} 1845:injective functions 1841:bijective functions 1824:If a monoid is not 1802:in a monoid form a 1800:invertible elements 1703:of a group element 1658:one. It is also an 1552:{\displaystyle x*y} 1526:{\displaystyle x*y} 1314:{\displaystyle -x.} 921:into the integers. 781:{\displaystyle e*f} 674:{\displaystyle e*f} 361:and composition of 152:When the operation 5746:identity functions 5726:Unit (ring theory) 5684: 5678: 5612: 5566: 5485: 5483: 5463: 5454: 5384: 5342: 5230: 5166: 5085: 5046: 4998: 4914: 4847: 4819: 4813: 4726: 4646: 4614: 4600: 4581: 4578: 4507: 4461: 4444: 4425: 4422: 4354: 4299: 4275: 4245: 4217: 4204:with entries in a 4194: 4141:Galois connections 3896:, the elements of 3649: 3620: 3584: 3427: 3329: 3227: 3184: 3160: 3140: 3112: 3092: 3072: 3052: 3028: 3008: 2984: 2964: 2932: 2900: 2871: 2840: 2815:split monomorphism 2749: 2696: 2664: 2640: 2606: 2575: 2549: 2509: 2246:field of fractions 2167: 2137: 2007:field of fractions 1987:Grothendieck group 1973: 1946: 1914: 1885: 1773:Rubik's cube group 1762:{\displaystyle g.} 1759: 1739:{\displaystyle g,} 1736: 1713: 1693: 1623:is also called an 1595: 1549: 1523: 1482: 1451: 1418: 1382: 1348: 1311: 1268: 1137:depending whether 1127: 1089: 1054: 1010: 984:{\displaystyle 2n} 981: 950: 856: 817:identity functions 778: 741: 700: 671: 623: 541: 481: 408:{\displaystyle *.} 405: 351:partial operations 339:invertible element 300: 298: 271: 269: 194:invertible element 186:invertible element 182:functional inverse 5890:Binary operations 5754:identity matrices 5515: 5470: 5401: 5298: 5266: 5247: 5192: 5111: 4948: 4894: 4875: 4854: 4717: 4690: 4588: 4557: 4538: 4529: 4527: 4432: 4415: 4388: 4373: 4371: 4302:{\displaystyle R} 4278:{\displaystyle R} 4257:invertible matrix 4248:{\displaystyle M} 4220:{\displaystyle K} 4197:{\displaystyle M} 4147:Galois connection 3910:absorbing element 3906:inverse semigroup 3860:Green's relations 3778:is an inverse of 3770:is an inverse of 3676:Regular semigroup 3630:, and denoted by 3623:{\displaystyle S} 3587:{\displaystyle *} 3574:If the operation 3569: 3568: 3403: 3402: 3298: 3297: 3187:{\displaystyle S} 3163:{\displaystyle S} 3143:{\displaystyle y} 3124:two-sided inverse 3115:{\displaystyle x} 3095:{\displaystyle y} 3075:{\displaystyle x} 3055:{\displaystyle a} 3031:{\displaystyle b} 3011:{\displaystyle b} 2987:{\displaystyle a} 2874:{\displaystyle *} 2843:{\displaystyle S} 2826:In a unital magma 2811:split epimorphism 2773:identity function 2759:for every object 2699:{\displaystyle f} 2667:{\displaystyle f} 2455:partial operation 2424:unimodular matrix 2381:invertible matrix 2368:are all equal to 2162: 2106:. The inverse or 2062:additive identity 2019:commutative rings 1787:is a set with an 1771:For example, the 1716:{\displaystyle g} 1533:is defined, then 1480: 1377: 1122: 1087: 1045: 930:doubling function 907:additive identity 788:is not defined. 681:is defined, then 605: 544:{\displaystyle *} 527:Identity elements 380:In this section, 343:binary operations 319:identity elements 297: 268: 231:is an invertible 221:inverse functions 5897: 5885:Abstract algebra 5840: 5793: 5792: 5785: 5779: 5776: 5770: 5767: 5761: 5742: 5693: 5691: 5690: 5685: 5683: 5682: 5617: 5616: 5571: 5570: 5517: 5516: 5513: 5494: 5492: 5491: 5486: 5484: 5479: 5471: 5468: 5459: 5458: 5402: 5394: 5389: 5388: 5347: 5346: 5299: 5291: 5282: 5281: 5273: 5269: 5268: 5267: 5264: 5249: 5248: 5245: 5235: 5234: 5193: 5185: 5180: 5179: 5171: 5170: 5127: 5126: 5118: 5114: 5113: 5112: 5109: 5090: 5089: 5051: 5050: 5003: 5002: 4950: 4949: 4946: 4923: 4921: 4920: 4915: 4910: 4909: 4901: 4897: 4896: 4895: 4892: 4877: 4876: 4873: 4863: 4855: 4852: 4828: 4826: 4825: 4820: 4818: 4817: 4735: 4733: 4732: 4727: 4719: 4718: 4715: 4709: 4708: 4700: 4696: 4692: 4691: 4688: 4664:and is given by 4655: 4653: 4652: 4647: 4623: 4621: 4620: 4615: 4613: 4612: 4599: 4597: 4589: 4586: 4579: 4574: 4573: 4572: 4564: 4560: 4559: 4558: 4555: 4540: 4539: 4536: 4516: 4514: 4513: 4508: 4470: 4468: 4467: 4462: 4460: 4459: 4443: 4441: 4433: 4430: 4423: 4418: 4417: 4416: 4413: 4407: 4406: 4398: 4394: 4390: 4389: 4386: 4363: 4361: 4360: 4355: 4308: 4306: 4305: 4300: 4284: 4282: 4281: 4276: 4264:commutative ring 4254: 4252: 4251: 4246: 4226: 4224: 4223: 4218: 4203: 4201: 4200: 4195: 3658: 3656: 3655: 3650: 3629: 3627: 3626: 3621: 3593: 3591: 3590: 3585: 3447: 3446: 3436: 3434: 3433: 3428: 3345: 3344: 3338: 3336: 3335: 3330: 3240: 3239: 3236: 3234: 3233: 3228: 3200:right invertible 3193: 3191: 3190: 3185: 3169: 3167: 3166: 3161: 3149: 3147: 3146: 3141: 3121: 3119: 3118: 3113: 3101: 3099: 3098: 3093: 3081: 3079: 3078: 3073: 3062:. If an element 3061: 3059: 3058: 3053: 3037: 3035: 3034: 3029: 3017: 3015: 3014: 3009: 2993: 2991: 2990: 2985: 2973: 2971: 2970: 2965: 2941: 2939: 2938: 2933: 2909: 2907: 2906: 2901: 2883:identity element 2880: 2878: 2877: 2872: 2860:binary operation 2849: 2847: 2846: 2841: 2784:inverse function 2762: 2758: 2756: 2755: 2750: 2736: 2735: 2713: 2705: 2703: 2702: 2697: 2681: 2673: 2671: 2670: 2665: 2649: 2647: 2646: 2641: 2636: 2615: 2613: 2612: 2607: 2599: 2584: 2582: 2581: 2576: 2559:the composition 2558: 2556: 2555: 2550: 2539: 2518: 2516: 2515: 2510: 2437: 2433: 2420:integer matrices 2413: 2398: 2394: 2386: 2375: 2371: 2355: 2345: 2341: 2331: 2327: 2323: 2319: 2309: 2291:commutative ring 2242:rational numbers 2235: 2226:commutative ring 2215:linear functions 2197: 2190: 2182: 2176: 2174: 2173: 2168: 2163: 2155: 2146: 2144: 2143: 2138: 2133: 2132: 2113: 2097: 2082: 2074:additive inverse 2071: 2067: 1999:rational numbers 1984: 1982: 1980: 1979: 1974: 1955: 1953: 1952: 1947: 1923: 1921: 1920: 1915: 1894: 1892: 1891: 1886: 1862: 1793:identity element 1768: 1766: 1765: 1760: 1745: 1743: 1742: 1737: 1722: 1720: 1719: 1714: 1702: 1700: 1699: 1694: 1692: 1691: 1619:, an invertible 1604: 1602: 1601: 1596: 1591: 1590: 1578: 1577: 1558: 1556: 1555: 1550: 1532: 1530: 1529: 1524: 1506: 1502: 1491: 1489: 1488: 1483: 1481: 1473: 1460: 1458: 1457: 1452: 1450: 1449: 1427: 1425: 1424: 1419: 1414: 1413: 1391: 1389: 1388: 1383: 1378: 1370: 1357: 1355: 1354: 1349: 1344: 1343: 1324: 1320: 1318: 1317: 1312: 1294: 1291:, of an element 1289:additive inverse 1277: 1275: 1274: 1269: 1197: 1193: 1189: 1141:is even or odd. 1140: 1136: 1134: 1133: 1128: 1123: 1118: 1107: 1098: 1096: 1095: 1090: 1088: 1080: 1071: 1063: 1061: 1060: 1055: 1050: 1046: 1038: 1019: 1017: 1016: 1011: 990: 988: 987: 982: 967: 959: 957: 956: 951: 915:additive inverse 912: 904: 893: 885: 881: 873: 869: 865: 863: 862: 857: 811: 804: 787: 785: 784: 779: 761: 757: 750: 748: 747: 742: 709: 707: 706: 701: 680: 678: 677: 672: 654: 650: 643: 639: 632: 630: 629: 624: 606: 603: 575: 565:identity element 558: 550: 548: 547: 542: 511: 507: 490: 488: 487: 482: 414: 412: 411: 406: 383: 375:identity element 333:The concepts of 309: 307: 306: 301: 299: 290: 280: 278: 277: 272: 270: 261: 217:inverse matrices 196:, also called a 174:additive inverse 163: 160:, if an element 155: 148: 144: 140: 126: 112: 104: 100: 92: 89:, one says that 88: 74: 69:identity element 66: 55: 44: 5905: 5904: 5900: 5899: 5898: 5896: 5895: 5894: 5870: 5869: 5864:Semigroup Forum 5857:Semigroup Forum 5851:Miyuki Yamada, 5837: 5827:Clarendon Press 5802: 5797: 5796: 5787: 5786: 5782: 5777: 5773: 5768: 5764: 5743: 5739: 5734: 5707: 5699:singular matrix 5677: 5676: 5671: 5666: 5660: 5659: 5654: 5649: 5643: 5642: 5637: 5632: 5622: 5621: 5611: 5610: 5605: 5600: 5594: 5593: 5588: 5583: 5573: 5572: 5565: 5564: 5559: 5553: 5552: 5547: 5541: 5540: 5535: 5525: 5524: 5512: 5508: 5506: 5503: 5502: 5482: 5481: 5472: 5467: 5453: 5452: 5444: 5438: 5437: 5432: 5423: 5422: 5417: 5404: 5403: 5393: 5383: 5382: 5377: 5368: 5367: 5359: 5349: 5348: 5341: 5340: 5335: 5329: 5328: 5323: 5317: 5316: 5311: 5301: 5300: 5290: 5283: 5274: 5263: 5259: 5255: 5251: 5250: 5244: 5240: 5237: 5236: 5229: 5228: 5223: 5214: 5213: 5205: 5195: 5194: 5184: 5172: 5165: 5164: 5159: 5153: 5152: 5147: 5137: 5136: 5135: 5128: 5119: 5108: 5104: 5100: 5096: 5095: 5092: 5091: 5084: 5083: 5078: 5072: 5071: 5066: 5056: 5055: 5045: 5044: 5039: 5033: 5032: 5027: 5021: 5020: 5015: 5005: 5004: 4997: 4996: 4991: 4986: 4980: 4979: 4974: 4969: 4959: 4958: 4951: 4945: 4941: 4934: 4932: 4929: 4928: 4902: 4891: 4887: 4883: 4879: 4878: 4872: 4868: 4856: 4851: 4845: 4842: 4841: 4812: 4811: 4806: 4801: 4795: 4794: 4789: 4784: 4774: 4773: 4753: 4750: 4749: 4714: 4710: 4701: 4687: 4683: 4682: 4678: 4677: 4669: 4666: 4665: 4632: 4629: 4628: 4608: 4604: 4590: 4585: 4580: 4565: 4554: 4550: 4546: 4542: 4541: 4535: 4531: 4530: 4528: 4522: 4519: 4518: 4478: 4475: 4474: 4455: 4451: 4434: 4429: 4424: 4412: 4408: 4399: 4385: 4381: 4380: 4376: 4375: 4374: 4372: 4369: 4366: 4365: 4325: 4322: 4321: 4294: 4291: 4290: 4270: 4267: 4266: 4240: 4237: 4236: 4212: 4209: 4208: 4189: 4186: 4185: 4179: 4143: 4135: 4130: 4124: 3932: 3902: 3890: 3878: 3871: 3688:In a semigroup 3678: 3672: 3665: 3635: 3632: 3631: 3615: 3612: 3611: 3579: 3576: 3575: 3410: 3407: 3406: 3312: 3309: 3308: 3210: 3207: 3206: 3196:left invertible 3179: 3176: 3175: 3155: 3152: 3151: 3135: 3132: 3131: 3126:, or simply an 3107: 3104: 3103: 3087: 3084: 3083: 3067: 3064: 3063: 3047: 3044: 3043: 3023: 3020: 3019: 3003: 3000: 2999: 2979: 2976: 2975: 2947: 2944: 2943: 2915: 2912: 2911: 2889: 2886: 2885: 2866: 2863: 2862: 2835: 2832: 2831: 2828: 2823: 2821:Generalizations 2760: 2731: 2727: 2725: 2722: 2721: 2711: 2691: 2688: 2687: 2679: 2659: 2656: 2655: 2629: 2621: 2618: 2617: 2592: 2590: 2587: 2586: 2564: 2561: 2560: 2532: 2524: 2521: 2520: 2492: 2489: 2488: 2448: 2435: 2431: 2418:In the case of 2411: 2396: 2392: 2384: 2373: 2369: 2358:identity matrix 2347: 2343: 2333: 2329: 2325: 2321: 2311: 2307: 2262: 2250:integral domain 2233: 2195: 2188: 2180: 2154: 2152: 2149: 2148: 2125: 2121: 2119: 2116: 2115: 2111: 2095: 2077: 2069: 2065: 2027: 2011:integral domain 1995:natural numbers 1962: 1959: 1958: 1957: 1929: 1926: 1925: 1900: 1897: 1896: 1868: 1865: 1864: 1860: 1781: 1751: 1748: 1747: 1728: 1725: 1724: 1708: 1705: 1704: 1684: 1680: 1678: 1675: 1674: 1671:transformations 1633: 1617:category theory 1583: 1579: 1570: 1566: 1564: 1561: 1560: 1538: 1535: 1534: 1512: 1509: 1508: 1504: 1500: 1472: 1470: 1467: 1466: 1439: 1435: 1433: 1430: 1429: 1403: 1399: 1397: 1394: 1393: 1369: 1367: 1364: 1363: 1362:multiplication 1336: 1332: 1330: 1327: 1326: 1322: 1300: 1297: 1296: 1292: 1206: 1203: 1202: 1195: 1191: 1187: 1177: 1161:category theory 1138: 1108: 1106: 1104: 1101: 1100: 1079: 1077: 1074: 1073: 1069: 1037: 1033: 1025: 1022: 1021: 996: 993: 992: 973: 970: 969: 965: 936: 933: 932: 919:natural numbers 910: 902: 891: 883: 879: 871: 867: 836: 833: 832: 829: 809: 806:identity matrix 796: 795:, there is one 767: 764: 763: 759: 755: 715: 712: 711: 686: 683: 682: 660: 657: 656: 652: 648: 641: 637: 602: 584: 581: 580: 573: 568:, or simply an 556: 536: 533: 532: 529: 509: 495: 434: 431: 430: 420: 397: 394: 393: 381: 335:inverse element 331: 326: 288: 286: 283: 282: 259: 257: 254: 253: 225:category theory 166:inverse element 161: 153: 146: 142: 128: 114: 110: 102: 98: 90: 76: 72: 64: 56:) of numbers. 50: 39: 32:inverse element 24: 17: 12: 11: 5: 5903: 5893: 5892: 5887: 5882: 5868: 5867: 5860: 5849: 5844:Drazin, M.P., 5842: 5835: 5818: 5801: 5798: 5795: 5794: 5780: 5771: 5762: 5736: 5735: 5733: 5730: 5729: 5728: 5723: 5721:Loop (algebra) 5718: 5713: 5706: 5703: 5695: 5694: 5681: 5675: 5672: 5670: 5667: 5665: 5662: 5661: 5658: 5655: 5653: 5650: 5648: 5645: 5644: 5641: 5638: 5636: 5633: 5631: 5628: 5627: 5625: 5620: 5615: 5609: 5606: 5604: 5601: 5599: 5596: 5595: 5592: 5589: 5587: 5584: 5582: 5579: 5578: 5576: 5569: 5563: 5560: 5558: 5555: 5554: 5551: 5548: 5546: 5543: 5542: 5539: 5536: 5534: 5531: 5530: 5528: 5523: 5520: 5511: 5496: 5495: 5478: 5475: 5466: 5462: 5457: 5451: 5448: 5445: 5443: 5440: 5439: 5436: 5433: 5431: 5428: 5425: 5424: 5421: 5418: 5416: 5413: 5410: 5409: 5407: 5400: 5397: 5392: 5387: 5381: 5378: 5376: 5373: 5370: 5369: 5366: 5363: 5360: 5358: 5355: 5354: 5352: 5345: 5339: 5336: 5334: 5331: 5330: 5327: 5324: 5322: 5319: 5318: 5315: 5312: 5310: 5307: 5306: 5304: 5297: 5294: 5289: 5286: 5284: 5280: 5277: 5272: 5262: 5258: 5254: 5243: 5239: 5238: 5233: 5227: 5224: 5222: 5219: 5216: 5215: 5212: 5209: 5206: 5204: 5201: 5200: 5198: 5191: 5188: 5183: 5178: 5175: 5169: 5163: 5160: 5158: 5155: 5154: 5151: 5148: 5146: 5143: 5142: 5140: 5134: 5131: 5129: 5125: 5122: 5117: 5107: 5103: 5099: 5094: 5093: 5088: 5082: 5079: 5077: 5074: 5073: 5070: 5067: 5065: 5062: 5061: 5059: 5054: 5049: 5043: 5040: 5038: 5035: 5034: 5031: 5028: 5026: 5023: 5022: 5019: 5016: 5014: 5011: 5010: 5008: 5001: 4995: 4992: 4990: 4987: 4985: 4982: 4981: 4978: 4975: 4973: 4970: 4968: 4965: 4964: 4962: 4957: 4954: 4952: 4944: 4940: 4937: 4936: 4913: 4908: 4905: 4900: 4890: 4886: 4882: 4871: 4867: 4862: 4859: 4850: 4830: 4829: 4816: 4810: 4807: 4805: 4802: 4800: 4797: 4796: 4793: 4790: 4788: 4785: 4783: 4780: 4779: 4777: 4772: 4769: 4766: 4763: 4760: 4757: 4740:rank deficient 4725: 4722: 4713: 4707: 4704: 4699: 4695: 4686: 4681: 4676: 4673: 4645: 4642: 4639: 4636: 4625: 4624: 4611: 4607: 4603: 4596: 4593: 4584: 4577: 4571: 4568: 4563: 4553: 4549: 4545: 4534: 4526: 4506: 4503: 4500: 4497: 4494: 4491: 4488: 4485: 4482: 4471: 4458: 4454: 4450: 4447: 4440: 4437: 4428: 4421: 4411: 4405: 4402: 4397: 4393: 4384: 4379: 4353: 4350: 4347: 4344: 4341: 4338: 4335: 4332: 4329: 4298: 4287:if and only if 4285:is invertible 4274: 4244: 4216: 4193: 4178: 4175: 4142: 4139: 4134: 4131: 4126:Main article: 4123: 4120: 4024: 4023: 3995: 3950:; this endows 3931: 3925: 3900: 3888: 3876: 3869: 3674:Main article: 3671: 3670:In a semigroup 3668: 3663: 3648: 3645: 3642: 3639: 3619: 3608:group of units 3583: 3567: 3566: 3563: 3560: 3557: 3554: 3551: 3547: 3546: 3543: 3540: 3537: 3534: 3531: 3527: 3526: 3523: 3520: 3517: 3514: 3511: 3507: 3506: 3503: 3500: 3497: 3494: 3491: 3487: 3486: 3483: 3480: 3477: 3474: 3471: 3467: 3466: 3463: 3460: 3457: 3454: 3451: 3426: 3423: 3420: 3417: 3414: 3401: 3400: 3397: 3394: 3391: 3387: 3386: 3383: 3380: 3377: 3373: 3372: 3369: 3366: 3363: 3359: 3358: 3355: 3352: 3349: 3328: 3325: 3322: 3319: 3316: 3296: 3295: 3292: 3289: 3286: 3282: 3281: 3278: 3275: 3272: 3268: 3267: 3264: 3261: 3258: 3254: 3253: 3250: 3247: 3244: 3226: 3223: 3220: 3217: 3214: 3183: 3159: 3139: 3111: 3091: 3071: 3051: 3027: 3007: 2983: 2963: 2960: 2957: 2954: 2951: 2931: 2928: 2925: 2922: 2919: 2899: 2896: 2893: 2870: 2839: 2827: 2824: 2822: 2819: 2748: 2745: 2742: 2739: 2734: 2730: 2695: 2663: 2639: 2635: 2632: 2628: 2625: 2605: 2602: 2598: 2595: 2574: 2571: 2568: 2548: 2545: 2542: 2538: 2535: 2531: 2528: 2508: 2505: 2502: 2499: 2496: 2447: 2444: 2401:inverse matrix 2346:is defined if 2328:columns), and 2293:are considered 2261: 2258: 2166: 2161: 2158: 2136: 2131: 2128: 2124: 2064:, and denoted 2043:multiplication 2026: 2023: 1972: 1969: 1966: 1945: 1942: 1939: 1936: 1933: 1913: 1910: 1907: 1904: 1884: 1881: 1878: 1875: 1872: 1819:group of units 1780: 1777: 1758: 1755: 1735: 1732: 1712: 1690: 1687: 1683: 1632: 1629: 1607:An invertible 1594: 1589: 1586: 1582: 1576: 1573: 1569: 1548: 1545: 1542: 1522: 1519: 1516: 1479: 1476: 1448: 1445: 1442: 1438: 1417: 1412: 1409: 1406: 1402: 1381: 1376: 1373: 1347: 1342: 1339: 1335: 1310: 1307: 1304: 1279: 1278: 1267: 1264: 1261: 1258: 1255: 1252: 1249: 1246: 1243: 1240: 1237: 1234: 1231: 1228: 1225: 1222: 1219: 1216: 1213: 1210: 1179:An element is 1176: 1173: 1126: 1121: 1117: 1114: 1111: 1086: 1083: 1066:floor function 1053: 1049: 1044: 1041: 1036: 1032: 1029: 1009: 1006: 1003: 1000: 980: 977: 949: 946: 943: 940: 855: 852: 849: 846: 843: 840: 828: 825: 777: 774: 771: 740: 737: 734: 731: 728: 725: 722: 719: 699: 696: 693: 690: 670: 667: 664: 634: 633: 622: 619: 616: 613: 610: 600: 597: 594: 591: 588: 572:is an element 551:be a possibly 540: 528: 525: 492: 491: 480: 477: 474: 471: 468: 465: 462: 459: 456: 453: 450: 447: 444: 441: 438: 419: 416: 404: 401: 330: 327: 296: 293: 267: 264: 168:or simply the 15: 9: 6: 4: 3: 2: 5902: 5891: 5888: 5886: 5883: 5881: 5878: 5877: 5875: 5865: 5861: 5858: 5854: 5850: 5847: 5843: 5838: 5836:0-19-851194-9 5832: 5828: 5824: 5819: 5816: 5815:3-11-015248-7 5812: 5808: 5804: 5803: 5790: 5784: 5775: 5766: 5759: 5755: 5751: 5747: 5741: 5737: 5727: 5724: 5722: 5719: 5717: 5714: 5712: 5711:Division ring 5709: 5708: 5702: 5700: 5679: 5673: 5668: 5663: 5656: 5651: 5646: 5639: 5634: 5629: 5623: 5618: 5613: 5607: 5602: 5597: 5590: 5585: 5580: 5574: 5567: 5561: 5556: 5549: 5544: 5537: 5532: 5526: 5521: 5518: 5509: 5501: 5500: 5499: 5476: 5473: 5464: 5460: 5455: 5449: 5446: 5441: 5434: 5429: 5426: 5419: 5414: 5411: 5405: 5398: 5395: 5390: 5385: 5379: 5374: 5371: 5364: 5361: 5356: 5350: 5343: 5337: 5332: 5325: 5320: 5313: 5308: 5302: 5295: 5292: 5287: 5285: 5278: 5275: 5270: 5260: 5256: 5252: 5241: 5231: 5225: 5220: 5217: 5210: 5207: 5202: 5196: 5189: 5186: 5181: 5176: 5173: 5167: 5161: 5156: 5149: 5144: 5138: 5132: 5130: 5123: 5120: 5115: 5105: 5101: 5097: 5086: 5080: 5075: 5068: 5063: 5057: 5052: 5047: 5041: 5036: 5029: 5024: 5017: 5012: 5006: 4999: 4993: 4988: 4983: 4976: 4971: 4966: 4960: 4955: 4953: 4942: 4938: 4927: 4926: 4925: 4911: 4906: 4903: 4898: 4888: 4884: 4880: 4869: 4865: 4860: 4857: 4848: 4839: 4835: 4814: 4808: 4803: 4798: 4791: 4786: 4781: 4775: 4770: 4767: 4764: 4761: 4758: 4755: 4748: 4747: 4746: 4743: 4741: 4736: 4723: 4720: 4711: 4705: 4702: 4697: 4693: 4684: 4679: 4674: 4671: 4663: 4659: 4658:least squares 4643: 4640: 4637: 4634: 4609: 4605: 4601: 4594: 4591: 4582: 4575: 4569: 4566: 4561: 4551: 4547: 4543: 4532: 4524: 4504: 4501: 4498: 4495: 4492: 4489: 4486: 4483: 4480: 4472: 4456: 4452: 4448: 4445: 4438: 4435: 4426: 4419: 4409: 4403: 4400: 4395: 4391: 4382: 4377: 4351: 4348: 4345: 4342: 4339: 4336: 4333: 4330: 4327: 4319: 4318: 4317: 4315: 4310: 4296: 4288: 4272: 4265: 4260: 4258: 4242: 4234: 4230: 4214: 4207: 4191: 4184: 4183:square matrix 4174: 4172: 4168: 4164: 4160: 4156: 4152: 4148: 4138: 4129: 4119: 4117: 4113: 4109: 4105: 4101: 4097: 4093: 4089: 4085: 4081: 4077: 4073: 4069: 4065: 4061: 4057: 4053: 4049: 4045: 4041: 4037: 4033: 4029: 4021: 4017: 4013: 4009: 4005: 4001: 4000: 3996: 3994: 3990: 3986: 3982: 3980: 3976: 3975: 3974: 3972: 3968: 3964: 3960: 3958: 3953: 3949: 3945: 3941: 3937: 3929: 3924: 3922: 3918: 3917:quasi-inverse 3913: 3911: 3907: 3899: 3895: 3891: 3887: 3881: 3879: 3872: 3865: 3861: 3857: 3853: 3849: 3845: 3841: 3837: 3833: 3829: 3825: 3821: 3817: 3813: 3809: 3805: 3801: 3797: 3793: 3789: 3785: 3781: 3777: 3773: 3769: 3765: 3761: 3757: 3753: 3749: 3745: 3741: 3737: 3733: 3729: 3726:. An element 3725: 3724: 3723:pseudoinverse 3719: 3715: 3711: 3707: 3703: 3699: 3695: 3691: 3686: 3684: 3677: 3667: 3662: 3643: 3637: 3617: 3609: 3606:, called the 3605: 3601: 3597: 3581: 3572: 3564: 3561: 3558: 3555: 3552: 3549: 3548: 3544: 3541: 3538: 3535: 3532: 3529: 3528: 3524: 3521: 3518: 3515: 3512: 3509: 3508: 3504: 3501: 3498: 3495: 3492: 3489: 3488: 3484: 3481: 3478: 3475: 3472: 3469: 3468: 3448: 3445: 3442: 3440: 3421: 3418: 3415: 3398: 3395: 3392: 3389: 3388: 3384: 3381: 3378: 3375: 3374: 3370: 3367: 3364: 3361: 3360: 3346: 3343: 3342: 3339:given by the 3323: 3320: 3317: 3306: 3301: 3293: 3290: 3287: 3284: 3283: 3279: 3276: 3273: 3270: 3269: 3265: 3262: 3259: 3256: 3255: 3241: 3238: 3221: 3218: 3215: 3203: 3201: 3197: 3181: 3173: 3157: 3137: 3129: 3125: 3109: 3089: 3069: 3049: 3041: 3040:right inverse 3025: 3005: 2997: 2981: 2961: 2958: 2955: 2952: 2949: 2929: 2926: 2923: 2920: 2917: 2897: 2894: 2891: 2884: 2868: 2861: 2857: 2854:, that is, a 2853: 2837: 2818: 2816: 2812: 2808: 2804: 2803:vector spaces 2800: 2796: 2791: 2789: 2785: 2781: 2776: 2774: 2770: 2766: 2746: 2740: 2737: 2732: 2728: 2720: 2715: 2709: 2693: 2685: 2677: 2661: 2653: 2637: 2633: 2630: 2626: 2623: 2603: 2600: 2596: 2593: 2572: 2569: 2566: 2546: 2543: 2536: 2533: 2529: 2526: 2506: 2500: 2497: 2494: 2485: 2483: 2478: 2476: 2472: 2468: 2464: 2460: 2459:homomorphisms 2456: 2452: 2443: 2439: 2429: 2425: 2421: 2416: 2408: 2406: 2405:Cramer's rule 2402: 2390: 2382: 2377: 2367: 2366:main diagonal 2363: 2362:square matrix 2359: 2354: 2350: 2340: 2336: 2318: 2314: 2304: 2302: 2298: 2294: 2292: 2286: 2282: 2278: 2274: 2270: 2266: 2257: 2255: 2251: 2247: 2243: 2239: 2231: 2230:zero divisors 2227: 2222: 2220: 2216: 2212: 2207: 2205: 2204:division ring 2201: 2192: 2186: 2177: 2164: 2159: 2156: 2134: 2129: 2126: 2122: 2109: 2105: 2101: 2093: 2089: 2084: 2081: 2076:and denoted 2075: 2063: 2059: 2055: 2051: 2050:abelian group 2046: 2044: 2040: 2036: 2032: 2022: 2020: 2016: 2015:localizations 2012: 2008: 2004: 2000: 1996: 1992: 1988: 1970: 1967: 1964: 1943: 1940: 1937: 1934: 1931: 1911: 1908: 1905: 1902: 1882: 1879: 1876: 1873: 1870: 1858: 1852: 1850: 1846: 1842: 1838: 1834: 1829: 1827: 1822: 1821:of the ring. 1820: 1817:and form the 1816: 1812: 1807: 1805: 1801: 1796: 1794: 1790: 1786: 1776: 1774: 1769: 1756: 1753: 1733: 1730: 1710: 1688: 1685: 1681: 1672: 1668: 1663: 1661: 1657: 1653: 1648: 1646: 1642: 1638: 1628: 1626: 1622: 1618: 1614: 1611:is called an 1610: 1605: 1592: 1587: 1584: 1580: 1574: 1571: 1567: 1546: 1543: 1540: 1520: 1517: 1514: 1497: 1495: 1477: 1474: 1464: 1446: 1443: 1440: 1436: 1428:The notation 1415: 1410: 1407: 1404: 1400: 1379: 1374: 1371: 1361: 1345: 1340: 1337: 1333: 1308: 1305: 1302: 1290: 1285: 1283: 1265: 1262: 1259: 1256: 1253: 1247: 1244: 1241: 1235: 1229: 1226: 1223: 1217: 1214: 1211: 1208: 1201: 1200: 1199: 1184: 1182: 1172: 1170: 1166: 1162: 1157: 1155: 1151: 1147: 1142: 1124: 1119: 1115: 1112: 1109: 1084: 1081: 1067: 1051: 1047: 1042: 1039: 1034: 1027: 1007: 1004: 1001: 998: 978: 975: 963: 947: 944: 938: 931: 927: 922: 920: 916: 908: 900: 895: 889: 888:right inverse 877: 853: 850: 847: 844: 841: 838: 824: 822: 818: 813: 807: 803: 799: 794: 789: 775: 772: 769: 752: 738: 735: 732: 729: 726: 723: 720: 717: 697: 694: 691: 688: 668: 665: 662: 645: 620: 617: 614: 611: 608: 598: 595: 592: 589: 586: 579: 578: 577: 571: 567: 566: 560: 554: 538: 524: 522: 518: 513: 506: 502: 498: 478: 475: 469: 466: 463: 457: 451: 448: 445: 439: 436: 429: 428: 427: 425: 418:Associativity 415: 402: 399: 391: 387: 378: 376: 372: 371:associativity 368: 364: 360: 356: 352: 348: 344: 340: 336: 324: 320: 316: 311: 294: 291: 265: 262: 251: 247: 246: 241: 236: 234: 230: 226: 222: 218: 214: 210: 206: 201: 199: 195: 191: 187: 183: 179: 175: 171: 167: 159: 150: 139: 135: 131: 125: 121: 117: 108: 107:right inverse 96: 87: 83: 79: 70: 63:denoted here 62: 57: 54: 48: 43: 37: 33: 29: 22: 5852: 5845: 5822: 5806: 5783: 5778:Howie p. 102 5774: 5765: 5740: 5696: 5497: 4837: 4833: 4831: 4744: 4737: 4660:formula for 4626: 4311: 4261: 4180: 4170: 4166: 4162: 4158: 4154: 4150: 4144: 4136: 4115: 4111: 4107: 4103: 4099: 4095: 4091: 4087: 4083: 4079: 4075: 4071: 4067: 4051: 4047: 4043: 4039: 4035: 4034:; these are 4027: 4025: 4019: 4011: 4007: 4003: 3999:*-semigroups 3997: 3992: 3988: 3984: 3978: 3977: 3970: 3966: 3962: 3956: 3955: 3951: 3947: 3943: 3939: 3935: 3933: 3927: 3916: 3914: 3897: 3893: 3885: 3882: 3874: 3867: 3863: 3855: 3851: 3847: 3843: 3839: 3835: 3831: 3827: 3823: 3819: 3815: 3811: 3807: 3803: 3795: 3791: 3787: 3783: 3779: 3775: 3771: 3767: 3763: 3759: 3755: 3751: 3747: 3743: 3739: 3735: 3731: 3727: 3721: 3717: 3713: 3709: 3705: 3701: 3697: 3693: 3689: 3687: 3679: 3660: 3573: 3570: 3443: 3439:Latin square 3404: 3341:Cayley table 3302: 3299: 3204: 3199: 3195: 3171: 3127: 3123: 3122:is called a 3039: 3038:is called a 2996:left inverse 2995: 2994:is called a 2850:be a unital 2829: 2805:but not for 2792: 2787: 2777: 2718: 2717:There is an 2716: 2486: 2479: 2474: 2449: 2440: 2428:real numbers 2417: 2409: 2378: 2352: 2348: 2338: 2334: 2316: 2312: 2305: 2288: 2263: 2238:localization 2223: 2208: 2193: 2187:, which has 2178: 2099: 2094:and denoted 2085: 2079: 2047: 2042: 2038: 2028: 1859:(an element 1853: 1830: 1823: 1808: 1799: 1797: 1791:that has an 1782: 1770: 1669:on a set as 1665:A group may 1664: 1649: 1634: 1609:homomorphism 1606: 1498: 1286: 1281: 1280: 1185: 1180: 1178: 1158: 1143: 929: 923: 901:, which has 896: 887: 876:left inverse 875: 830: 814: 801: 797: 790: 753: 646: 635: 569: 563: 561: 530: 514: 504: 500: 496: 493: 421: 390:proper class 388:(possibly a 379: 338: 334: 332: 237: 202: 193: 185: 169: 165: 151: 137: 133: 129: 123: 119: 115: 106: 95:left inverse 94: 85: 81: 77: 58: 52: 41: 31: 25: 5697:which is a 4233:determinant 3981:-semigroups 3930:-semigroups 3800:idempotents 3692:an element 3596:associative 2706:equals the 2482:associative 2475:composition 2451:Composition 2301:determinant 2287:. However, 2221:to itself. 2206:otherwise. 2114:is denoted 2058:associative 2054:commutative 1826:commutative 1625:isomorphism 1613:isomorphism 1360:commutative 1295:is denoted 1282:The inverse 1169:retractions 815:Similarly, 576:such that 424:associative 315:associative 229:isomorphism 158:associative 101:, and that 28:mathematics 5874:Categories 5800:References 4662:regression 4259:for more. 4078:such that 4016:involution 3959:-semigroup 3802:, that is 3708:such that 3696:is called 3172:invertible 3170:is called 2942:, we have 2910:. If, for 2799:surjective 2471:categories 1779:In monoids 1660:involution 1181:invertible 1154:surjective 1068:that maps 968:to either 636:for every 494:for every 47:reciprocal 5474:− 5447:− 5427:− 5412:− 5372:− 5362:− 5276:− 5218:− 5208:− 5174:− 5121:− 4904:− 4858:− 4765:× 4703:− 4592:− 4576:⏟ 4567:− 4496:∣ 4490:× 4436:− 4420:⏟ 4401:− 4343:∣ 4337:× 4314:full rank 4122:Semirings 3683:semigroup 3582:∗ 3422:∗ 3324:∗ 3222:∗ 2953:∗ 2927:∈ 2895:∈ 2869:∗ 2795:injective 2780:bijection 2744:→ 2738:: 2627:⊂ 2570:∘ 2541:→ 2530:: 2504:→ 2498:: 2467:morphisms 2324:rows and 2285:semirings 2185:zero ring 2127:− 1833:functions 1686:− 1631:In groups 1585:− 1572:− 1544:∗ 1518:∗ 1444:− 1441:∘ 1408:− 1405:∗ 1338:− 1303:− 1254:∗ 1245:∗ 1227:∗ 1218:∗ 1150:injective 1113:− 1031:↦ 942:↦ 926:functions 842:∗ 773:∗ 727:∗ 666:∗ 612:∗ 590:∗ 539:∗ 476:∗ 467:∗ 449:∗ 440:∗ 400:∗ 363:morphisms 317:and have 250:fractions 67:, and an 61:operation 59:Given an 5705:See also 4133:Examples 3942:for all 3850:, while 2719:identity 2684:codomain 2652:codomain 2634:′ 2597:′ 2537:′ 2269:matrices 2260:Matrices 2039:addition 2025:In rings 2003:integers 1991:integers 1956:implies 1895:implies 1652:function 1643:with an 1621:morphism 1465:, since 1198:, then 1175:Inverses 1165:sections 1048:⌋ 1035:⌊ 570:identity 367:category 245:inversus 233:morphism 141:for all 71:denoted 36:opposite 5880:Algebra 4832:So, as 3732:inverse 3128:inverse 3102:, then 2974:, then 2881:and an 2858:with a 2807:modules 2271:over a 2254:subring 2217:from a 1615:. In 553:partial 170:inverse 5833:  5813:  5752:, and 3938:°)° = 3842:, and 3600:monoid 2769:object 2708:domain 2676:domain 2248:of an 2088:monoid 2033:is an 2013:, and 2009:of an 1785:monoid 909:, and 882:, and 866:where 347:domain 205:groups 180:, and 45:) and 5732:Notes 5469:right 4853:right 4836:< 4587:right 4206:field 4106:)* = 4098:)* = 4094:, ( 4006:)° = 3782:then 3604:group 3130:, of 2852:magma 2813:or a 2453:is a 2332:is a 2310:is a 2277:rings 2273:field 2209:In a 2200:field 2098:. An 2001:from 1993:from 1815:units 1804:group 1656:arity 1639:is a 1637:group 886:is a 874:is a 384:is a 365:in a 240:Latin 213:units 209:rings 192:, an 105:is a 93:is a 75:, if 5831:ISBN 5811:ISBN 4502:< 4473:For 4431:left 4349:> 4320:For 4165:and 4153:and 4042:° = 3810:and 3798:are 3790:and 3746:and 3305:loop 3018:and 2830:Let 2519:and 2465:and 2391:in 2389:unit 2299:and 2297:rank 2283:and 2281:rngs 2104:unit 2056:and 2041:and 2031:ring 1924:and 1811:ring 1798:The 1503:and 1190:and 1064:the 758:and 651:and 640:and 531:Let 426:if 373:and 337:and 219:and 198:unit 190:ring 145:and 127:and 4738:No 4167:GLG 4159:LGL 4114:or 4102:, ( 4088:yxy 4080:xyx 3946:in 3923:). 3768:zxz 3760:xzx 3752:yxy 3740:xyx 3738:if 3734:of 3710:xzx 3704:in 3659:or 3610:of 3594:is 3198:or 3174:in 3042:of 2998:of 2856:set 2797:or 2765:set 2710:of 2686:of 2678:of 2654:of 2487:If 2469:of 2461:of 2434:or 2410:If 2407:. 2379:An 2306:If 2194:If 2017:of 1667:act 1641:set 1499:If 1159:In 1156:. 1099:or 1072:to 991:or 905:as 890:of 878:of 831:If 647:If 604:and 562:An 508:in 386:set 310:). 281:is 156:is 109:of 97:of 26:In 5876:: 5855:, 5829:. 5825:. 5674:45 5669:36 5664:27 5657:36 5652:29 5647:22 5640:27 5635:22 5630:17 5442:13 5415:17 5399:18 5380:14 5375:32 5365:32 5357:77 5296:54 5226:14 5221:32 5211:32 5203:77 5190:54 5162:77 5157:32 5150:32 5145:14 5081:77 5076:32 5069:32 5064:14 4309:. 4181:A 4169:= 4161:= 4149:, 4118:. 4108:yx 4104:yx 4100:xy 4096:xy 4090:= 4086:, 4082:= 4040:aa 4004:ab 3991:= 3985:aa 3838:= 3836:fy 3834:= 3832:ye 3830:, 3826:= 3824:xf 3822:= 3820:ex 3814:= 3812:ff 3806:= 3804:ee 3796:yx 3794:= 3788:xy 3786:= 3766:= 3758:= 3750:= 3742:= 3716:; 3712:= 3685:. 3666:. 3565:3 3562:2 3559:4 3556:1 3553:5 3550:5 3545:1 3542:3 3539:2 3536:5 3533:4 3530:4 3525:2 3522:1 3519:5 3516:4 3513:3 3510:3 3505:4 3502:5 3499:1 3496:3 3493:2 3490:2 3485:5 3482:4 3479:3 3476:2 3473:1 3470:1 3465:5 3462:4 3459:3 3456:2 3453:1 3450:* 3441:. 3399:1 3396:2 3393:3 3390:3 3385:2 3382:1 3379:2 3376:2 3371:3 3368:2 3365:1 3362:1 3357:3 3354:2 3351:1 3348:* 3294:1 3291:1 3288:3 3285:3 3280:1 3277:1 3274:2 3271:2 3266:3 3263:2 3260:1 3257:1 3252:3 3249:2 3246:1 3243:* 3202:. 2790:. 2729:id 2714:. 2484:. 2436:−1 2376:. 2351:= 2344:AB 2303:. 2279:, 2224:A 2029:A 2021:. 1997:, 1983:). 1851:. 1809:A 1795:. 1783:A 1635:A 1627:. 1496:. 1171:. 894:. 751:) 559:. 523:. 503:, 499:, 357:, 242:: 235:. 176:, 136:= 132:* 122:= 118:* 84:= 80:∗ 51:1/ 5839:. 5791:. 5760:. 5680:] 5624:[ 5619:= 5614:] 5608:6 5603:5 5598:4 5591:3 5586:2 5581:1 5575:[ 5568:] 5562:6 5557:3 5550:5 5545:2 5538:4 5533:1 5527:[ 5522:= 5519:A 5514:T 5510:A 5477:1 5465:A 5461:= 5456:] 5450:4 5435:2 5430:2 5420:8 5406:[ 5396:1 5391:= 5386:] 5351:[ 5344:] 5338:6 5333:3 5326:5 5321:2 5314:4 5309:1 5303:[ 5293:1 5288:= 5279:1 5271:) 5265:T 5261:A 5257:A 5253:( 5246:T 5242:A 5232:] 5197:[ 5187:1 5182:= 5177:1 5168:] 5139:[ 5133:= 5124:1 5116:) 5110:T 5106:A 5102:A 5098:( 5087:] 5058:[ 5053:= 5048:] 5042:6 5037:3 5030:5 5025:2 5018:4 5013:1 5007:[ 5000:] 4994:6 4989:5 4984:4 4977:3 4972:2 4967:1 4961:[ 4956:= 4947:T 4943:A 4939:A 4912:. 4907:1 4899:) 4893:T 4889:A 4885:A 4881:( 4874:T 4870:A 4866:= 4861:1 4849:A 4838:n 4834:m 4815:] 4809:6 4804:5 4799:4 4792:3 4787:2 4782:1 4776:[ 4771:= 4768:3 4762:2 4759:: 4756:A 4724:. 4721:b 4716:T 4712:A 4706:1 4698:) 4694:A 4689:T 4685:A 4680:( 4675:= 4672:x 4644:b 4641:= 4638:x 4635:A 4610:m 4606:I 4602:= 4595:1 4583:A 4570:1 4562:) 4556:T 4552:A 4548:A 4544:( 4537:T 4533:A 4525:A 4505:n 4499:m 4493:n 4487:m 4484:: 4481:A 4457:n 4453:I 4449:= 4446:A 4439:1 4427:A 4414:T 4410:A 4404:1 4396:) 4392:A 4387:T 4383:A 4378:( 4352:n 4346:m 4340:n 4334:m 4331:: 4328:A 4297:R 4273:R 4243:M 4215:K 4192:M 4171:G 4163:L 4155:G 4151:L 4092:y 4084:x 4076:y 4072:x 4068:a 4052:a 4048:a 4046:° 4044:a 4036:I 4028:I 4022:* 4020:a 4012:a 4010:° 4008:b 3993:a 3989:a 3987:° 3979:I 3971:U 3967:a 3963:a 3957:U 3952:S 3948:S 3944:a 3940:a 3936:a 3928:U 3901:e 3898:H 3894:e 3889:1 3886:H 3877:e 3875:L 3870:e 3868:R 3864:e 3856:y 3852:f 3848:x 3844:e 3840:y 3828:x 3816:f 3808:e 3792:f 3784:e 3780:x 3776:y 3772:x 3764:y 3756:x 3748:y 3744:x 3736:x 3728:y 3718:z 3714:x 3706:S 3702:z 3694:x 3690:S 3664:1 3661:H 3647:) 3644:S 3641:( 3638:U 3618:S 3425:) 3419:, 3416:S 3413:( 3327:) 3321:, 3318:S 3315:( 3225:) 3219:, 3216:S 3213:( 3182:S 3158:S 3138:y 3110:x 3090:y 3070:x 3050:a 3026:b 3006:b 2982:a 2962:e 2959:= 2956:b 2950:a 2930:S 2924:b 2921:, 2918:a 2898:S 2892:e 2838:S 2763:( 2761:X 2747:X 2741:X 2733:X 2712:g 2694:f 2680:g 2662:f 2638:. 2631:Y 2624:Y 2604:Y 2601:= 2594:Y 2573:f 2567:g 2547:, 2544:Z 2534:Y 2527:g 2507:Y 2501:X 2495:f 2432:1 2412:R 2397:R 2393:R 2385:R 2374:0 2370:1 2353:p 2349:n 2339:q 2337:× 2335:p 2330:B 2326:n 2322:m 2317:n 2315:× 2313:m 2308:A 2234:0 2196:0 2189:0 2181:0 2165:. 2160:x 2157:1 2135:, 2130:1 2123:x 2112:x 2096:1 2080:x 2078:− 2070:x 2066:0 1971:z 1968:= 1965:y 1944:x 1941:z 1938:= 1935:x 1932:y 1912:, 1909:z 1906:= 1903:y 1883:z 1880:x 1877:= 1874:y 1871:x 1861:x 1757:. 1754:g 1734:, 1731:g 1711:g 1689:1 1682:g 1593:. 1588:1 1581:x 1575:1 1568:y 1547:y 1541:x 1521:y 1515:x 1505:y 1501:x 1478:f 1475:1 1447:1 1437:f 1416:. 1411:1 1401:x 1380:. 1375:x 1372:1 1346:, 1341:1 1334:x 1323:x 1309:. 1306:x 1293:x 1266:. 1263:r 1260:= 1257:r 1251:) 1248:x 1242:l 1239:( 1236:= 1233:) 1230:r 1224:x 1221:( 1215:l 1212:= 1209:l 1196:x 1192:r 1188:l 1139:n 1125:, 1120:2 1116:1 1110:n 1085:2 1082:n 1070:n 1052:, 1043:2 1040:n 1028:n 1008:1 1005:+ 1002:n 999:2 979:n 976:2 966:n 948:x 945:2 939:x 911:0 903:0 892:x 884:y 880:y 872:x 868:e 854:, 851:e 848:= 845:y 839:x 810:n 802:n 800:× 798:n 776:f 770:e 760:f 756:e 739:. 736:f 733:= 730:f 724:e 721:= 718:e 698:. 695:f 692:= 689:e 669:f 663:e 653:f 649:e 642:y 638:x 621:y 618:= 615:y 609:e 599:x 596:= 593:e 587:x 574:e 557:X 510:X 505:z 501:y 497:x 479:z 473:) 470:y 464:x 461:( 458:= 455:) 452:z 446:y 443:( 437:x 403:. 382:X 325:. 295:x 292:y 266:y 263:x 162:x 154:∗ 147:y 143:x 138:y 134:y 130:e 124:x 120:e 116:x 111:x 103:y 99:y 91:x 86:e 82:y 78:x 73:e 65:∗ 53:x 49:( 42:x 40:− 38:( 23:.

Index

Invertible (disambiguation)
mathematics
opposite
reciprocal
operation
identity element
associative
additive inverse
multiplicative inverse
functional inverse
ring
unit
groups
rings
units
inverse matrices
inverse functions
category theory
isomorphism
morphism
Latin
inversus
fractions
associative
identity elements
§ Generalizations
binary operations
domain
partial operations
matrix multiplication

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