Theorem oncardval 7199

Description: The value of the cardinal number function with an ordinal number as its argument. (Contributed by NM, 24-Nov-2003.) (Revised by Mario Carneiro, 13-Sep-2013.)

Assertion

Ref	Expression
oncardval	|- ( A e. On -> ( card ` A ) = |^| { x e. On | x ~~ A } )

Distinct variable group:   x, A

Proof of Theorem oncardval

Dummy variable y is distinct from all other variables.

Step	Hyp	Ref	Expression
1		enrefg 6778	. . 3 |- ( A e. On -> A ~~ A )
2		breq1 4018	. . . 4 |- ( y = A -> ( y ~~ A <-> A ~~ A ) )
3	2	rspcev 2853	. . 3 |- ( ( A e. On /\ A ~~ A ) -> E. y e. On y ~~ A )
4	1, 3	mpdan 421	. 2 |- ( A e. On -> E. y e. On y ~~ A )
5		cardval3ex 7198	. 2 |- ( E. y e. On y ~~ A -> ( card ` A ) = |^| { x e. On | x ~~ A } )
6	4, 5	syl 14	1 |- ( A e. On -> ( card ` A ) = |^| { x e. On | x ~~ A } )

Syntax hints:   -> wi 4   = wceq 1363   e. wcel 2158   E.wrex 2466   {crab 2469   |^|cint 3856   class class class wbr 4015   Oncon0 4375   ` cfv 5228   ~~ cen 6752   cardccrd 7192

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-ia1 106  ax-ia2 107  ax-ia3 108  ax-io 710  ax-5 1457  ax-7 1458  ax-gen 1459  ax-ie1 1503  ax-ie2 1504  ax-8 1514  ax-10 1515  ax-11 1516  ax-i12 1517  ax-bndl 1519  ax-4 1520  ax-17 1536  ax-i9 1540  ax-ial 1544  ax-i5r 1545  ax-13 2160  ax-14 2161  ax-ext 2169  ax-sep 4133  ax-pow 4186  ax-pr 4221  ax-un 4445

This theorem depends on definitions:  df-bi 117  df-3an 981  df-tru 1366  df-nf 1471  df-sb 1773  df-eu 2039  df-mo 2040  df-clab 2174  df-cleq 2180  df-clel 2183  df-nfc 2318  df-ral 2470  df-rex 2471  df-rab 2474  df-v 2751  df-sbc 2975  df-un 3145  df-in 3147  df-ss 3154  df-pw 3589  df-sn 3610  df-pr 3611  df-op 3613  df-uni 3822  df-int 3857  df-br 4016  df-opab 4077  df-mpt 4078  df-id 4305  df-xp 4644  df-rel 4645  df-cnv 4646  df-co 4647  df-dm 4648  df-rn 4649  df-res 4650  df-ima 4651  df-iota 5190  df-fun 5230  df-fn 5231  df-f 5232  df-f1 5233  df-fo 5234  df-f1o 5235  df-fv 5236  df-en 6755  df-card 7193

This theorem is referenced by:  cardonle  7200