Theorem erexb 7767

Description: An equivalence relation is a set if and only if its domain is a set. (Contributed by Rodolfo Medina, 15-Oct-2010.) (Revised by Mario Carneiro, 12-Aug-2015.)

Assertion

Ref	Expression
erexb	|- ( R Er A -> ( R e. _V <-> A e. _V ) )

Proof of Theorem erexb

Step	Hyp	Ref	Expression
1		dmexg 7097	. . 3 |- ( R e. _V -> dom R e. _V )
2		erdm 7752	. . . 4 |- ( R Er A -> dom R = A )
3	2	eleq1d 2686	. . 3 |- ( R Er A -> ( dom R e. _V <-> A e. _V ) )
4	1, 3	syl5ib 234	. 2 |- ( R Er A -> ( R e. _V -> A e. _V ) )
5		erex 7766	. 2 |- ( R Er A -> ( A e. _V -> R e. _V ) )
6	4, 5	impbid 202	1 |- ( R Er A -> ( R e. _V <-> A e. _V ) )

Syntax hints:   -> wi 4   <-> wb 196   e. wcel 1990   _Vcvv 3200   dom cdm 5114   Er wer 7739

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1722  ax-4 1737  ax-5 1839  ax-6 1888  ax-7 1935  ax-8 1992  ax-9 1999  ax-10 2019  ax-11 2034  ax-12 2047  ax-13 2246  ax-ext 2602  ax-sep 4781  ax-nul 4789  ax-pow 4843  ax-pr 4906  ax-un 6949

This theorem depends on definitions:  df-bi 197  df-or 385  df-an 386  df-3an 1039  df-tru 1486  df-ex 1705  df-nf 1710  df-sb 1881  df-eu 2474  df-mo 2475  df-clab 2609  df-cleq 2615  df-clel 2618  df-nfc 2753  df-ral 2917  df-rex 2918  df-rab 2921  df-v 3202  df-dif 3577  df-un 3579  df-in 3581  df-ss 3588  df-nul 3916  df-if 4087  df-pw 4160  df-sn 4178  df-pr 4180  df-op 4184  df-uni 4437  df-br 4654  df-opab 4713  df-xp 5120  df-rel 5121  df-cnv 5122  df-dm 5124  df-rn 5125  df-er 7742

This theorem is referenced by:  prtex  34165