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Identity function

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The element 0 is usually referred to as the identity element and if it exists, it is unique
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In mathematics, a function that always returns the same value that was used as its argument
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to be this identity element. Such a definition generalizes to the concept of an
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A First Course in Topology: An Introduction to Mathematical Thinking
614:...then the diagonal set determined by M is the identity relation... 40: 808:
Conferences, University of Michigan Engineering Summer (1968).
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we see that an identity element of a semigroup is idempotent.
373:, one can alternately define the identity function on 267:, where a function is defined as a particular kind of 602:. American Mathematical Society. 1974. p. 92. 79:that always returns the value that was used as its 457:(essentially multiplication by 1), considered in 712:. Undergraduate Texts in Mathematics. Springer. 693:Elementary Linear Algebra (Applications Version) 576:(11th ed.). Sarat Book House. p. 36. 811:Foundations of Information Systems Engineering 661:Rosales, J. C.; García-Sánchez, P. A. (1999). 484:containing only this isometry (symmetry type 8: 428:the identity function is represented by the 733:D. Marshall; E. Odell; M. Starbird (2007). 599:Proceedings of Symposia in Pure Mathematics 709:Applied Linear Algebra and Matrix Analysis 369:Since the identity element of a monoid is 271:, the identity function is given by the 204:is always the same as the input element 540: 664:Finitely Generated Commutative Monoids 468:the identity function is trivially an 449:The identity function on the positive 7: 787:. Courier Corporation. p. 65. 695:(9th ed.), Wiley International 572:Mapa, Sadhan Kumar (7 April 2014). 187:In other words, the function value 574:Higher Algebra Abstract and Linear 498:, the identity function is always 455:completely multiplicative function 25: 781:Conover, Robert A. (2014-05-21). 142:is defined to be a function with 48:of the identity function on the 667:. Nova Publishers. p. 1. 366:(under function composition). 87:is the identity function, the 1: 735:Number Theory through Inquiry 172:  for all elements 844:Basic concepts in set theory 406:The identity function is a 216:. The identity function on 83:, unchanged. That is, when 870: 548:Knapp, Anthony W. (2006), 228:(its codomain is also its 104:is true for all values of 29: 638:10.1007/978-3-319-31159-3 505:The identity function is 472:. An object without any 130:, the identity function 30:Not to be confused with 397:need not be functions. 73:identity transformation 839:Elementary mathematics 834:Functions and mappings 691:Anton, Howard (2005), 354:of all functions from 307:is any function, then 239:The identity function 52: 706:T. S. Shores (2007). 446:chosen for the space. 44: 442:, regardless of the 335:function composition 333:, where "∘" denotes 289:Algebraic properties 251:is often denoted by 762:Hyperbolic Geometry 626:Nel, Louis (2016). 226:surjective function 849:Types of functions 530:Indicator function 222:injective function 53: 794:978-0-486-78001-6 764:, Springer 2005, 758:James W. Anderson 719:978-038-733-195-9 674:978-1-56072-670-8 647:978-3-319-31159-3 629:Continuity Theory 609:978-0-8218-1425-3 583:978-93-80663-24-1 559:978-0-8176-3248-9 496:topological space 381:identity morphism 337:. In particular, 273:identity relation 65:identity relation 63:, also called an 61:identity function 18:Identity operator 16:(Redirected from 861: 819: 818: 805: 799: 798: 778: 772: 759: 755: 749: 748: 730: 724: 723: 703: 697: 696: 688: 682: 681: 658: 652: 651: 623: 617: 616: 594: 588: 587: 569: 563: 562: 545: 490: 441: 420: 410:when applied to 396: 378: 365: 359: 348:identity element 345: 332: 306: 284: 259: 250: 244: 219: 215: 209: 203: 198:in the codomain 197: 183: 177: 171: 147: 141: 135: 125: 112:can be applied. 111: 107: 103: 86: 21: 869: 868: 864: 863: 862: 860: 859: 858: 824: 823: 822: 807: 806: 802: 795: 780: 779: 775: 757: 756: 752: 745: 732: 731: 727: 720: 705: 704: 700: 690: 689: 685: 675: 660: 659: 655: 648: 625: 624: 620: 610: 596: 595: 591: 584: 571: 570: 566: 560: 547: 546: 542: 538: 520:Identity matrix 516: 489: 485: 440: 432: 430:identity matrix 418: 408:linear operator 403: 392: 385:category theory 374: 361: 355: 344: 338: 327: 317: 308: 294: 291: 280: 269:binary relation 258: 252: 246: 240: 217: 211: 205: 199: 188: 185: 179: 173: 159: 143: 137: 131: 121: 118: 109: 105: 91: 84: 39: 28: 23: 22: 15: 12: 11: 5: 867: 865: 857: 856: 851: 846: 841: 836: 826: 825: 821: 820: 800: 793: 773: 750: 744:978-0883857519 743: 725: 718: 698: 683: 673: 653: 646: 632:. p. 21. 618: 608: 589: 582: 564: 558: 539: 537: 534: 533: 532: 527: 522: 515: 512: 511: 510: 503: 492: 487: 478:symmetry group 462: 447: 436: 415: 402: 399: 340: 323: 313: 290: 287: 254: 220:is clearly an 210:in the domain 158: 117: 114: 36:Empty function 26: 24: 14: 13: 10: 9: 6: 4: 3: 2: 866: 855: 852: 850: 847: 845: 842: 840: 837: 835: 832: 831: 829: 817: 813: 812: 804: 801: 796: 790: 786: 785: 777: 774: 771: 770:1-85233-934-9 767: 763: 754: 751: 746: 740: 736: 729: 726: 721: 715: 711: 710: 702: 699: 694: 687: 684: 680: 676: 670: 666: 665: 657: 654: 649: 643: 639: 635: 631: 630: 622: 619: 615: 611: 605: 601: 600: 593: 590: 585: 579: 575: 568: 565: 561: 555: 551: 550:Basic algebra 544: 541: 535: 531: 528: 526: 525:Inclusion map 523: 521: 518: 517: 513: 508: 504: 501: 497: 493: 483: 482:trivial group 479: 475: 471: 467: 463: 460: 459:number theory 456: 452: 448: 445: 439: 435: 431: 427: 424: 416: 413: 412:vector spaces 409: 405: 404: 400: 398: 395: 390: 389:endomorphisms 386: 382: 377: 372: 367: 364: 358: 353: 349: 343: 336: 331: 326: 321: 316: 311: 305: 301: 297: 288: 286: 283: 278: 274: 270: 266: 261: 257: 249: 243: 237: 235: 231: 227: 224:as well as a 223: 214: 208: 202: 195: 191: 182: 176: 170: 166: 162: 157: 156:, satisfying 155: 151: 146: 140: 134: 129: 124: 120:Formally, if 115: 113: 102: 98: 94: 90: 82: 78: 74: 70: 66: 62: 58: 51: 47: 43: 37: 33: 32:Null function 19: 815: 810: 803: 783: 776: 761: 753: 734: 728: 708: 701: 692: 686: 678: 663: 656: 628: 621: 613: 598: 592: 573: 567: 552:, Springer, 549: 543: 466:metric space 437: 433: 426:vector space 393: 387:, where the 375: 368: 362: 356: 341: 329: 324: 319: 314: 309: 303: 299: 295: 292: 281: 276: 262: 255: 247: 241: 238: 232:), so it is 212: 206: 200: 193: 189: 186: 180: 174: 168: 164: 160: 144: 138: 132: 122: 119: 100: 96: 92: 72: 69:identity map 68: 64: 60: 54: 50:real numbers 476:has as its 423:dimensional 57:mathematics 854:1 (number) 828:Categories 536:References 507:idempotent 500:continuous 401:Properties 265:set theory 116:Definition 234:bijective 108:to which 514:See also 474:symmetry 470:isometry 451:integers 298: : 277:diagonal 154:codomain 89:equality 81:argument 77:function 350:of the 346:is the 148:as its 75:, is a 791:  768:  741:  716:  671:  644:  606:  580:  556:  417:In an 371:unique 352:monoid 150:domain 494:In a 464:In a 453:is a 444:basis 275:, or 230:range 126:is a 59:, an 46:Graph 789:ISBN 766:ISBN 739:ISBN 714:ISBN 669:ISBN 642:ISBN 604:ISBN 578:ISBN 554:ISBN 480:the 322:= id 312:∘ id 167:) = 152:and 99:) = 634:doi 391:of 383:in 360:to 293:If 279:of 263:In 245:on 178:in 136:on 128:set 71:or 55:In 34:or 830:: 814:. 760:, 677:. 640:. 612:. 491:). 339:id 328:∘ 318:= 302:→ 285:. 260:. 253:id 236:. 67:, 797:. 747:. 722:. 650:. 636:: 586:. 509:. 502:. 488:1 486:C 461:. 438:n 434:I 421:- 419:n 414:. 394:M 376:M 363:X 357:X 342:X 330:f 325:Y 320:f 315:X 310:f 304:Y 300:X 296:f 282:X 256:X 248:X 242:f 218:X 213:X 207:x 201:X 196:) 194:x 192:( 190:f 184:. 181:X 175:x 169:x 165:x 163:( 161:f 145:X 139:X 133:f 123:X 110:f 106:x 101:x 97:x 95:( 93:f 85:f 38:. 20:)

Index

Identity operator
Null function
Empty function

Graph
real numbers
mathematics
function
argument
equality
set
domain
codomain
injective function
surjective function
range
bijective
set theory
binary relation
identity relation
function composition
identity element
monoid
unique
identity morphism
category theory
endomorphisms
linear operator
vector spaces
dimensional

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