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Theorem erexb 8171
 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 ∈ V ↔ 𝐴 ∈ V))

Proof of Theorem erexb
StepHypRef Expression
1 dmexg 7476 . . 3 (𝑅 ∈ V → dom 𝑅 ∈ V)
2 erdm 8156 . . . 4 (𝑅 Er 𝐴 → dom 𝑅 = 𝐴)
32eleq1d 2869 . . 3 (𝑅 Er 𝐴 → (dom 𝑅 ∈ V ↔ 𝐴 ∈ V))
41, 3syl5ib 245 . 2 (𝑅 Er 𝐴 → (𝑅 ∈ V → 𝐴 ∈ V))
5 erex 8170 . 2 (𝑅 Er 𝐴 → (𝐴 ∈ V → 𝑅 ∈ V))
64, 5impbid 213 1 (𝑅 Er 𝐴 → (𝑅 ∈ V ↔ 𝐴 ∈ V))
 Colors of variables: wff setvar class Syntax hints:   → wi 4   ↔ wb 207   ∈ wcel 2083  Vcvv 3440  dom cdm 5450   Er wer 8143 This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1781  ax-4 1795  ax-5 1892  ax-6 1951  ax-7 1996  ax-8 2085  ax-9 2093  ax-10 2114  ax-11 2128  ax-12 2143  ax-13 2346  ax-ext 2771  ax-sep 5101  ax-nul 5108  ax-pow 5164  ax-pr 5228  ax-un 7326 This theorem depends on definitions:  df-bi 208  df-an 397  df-or 843  df-3an 1082  df-tru 1528  df-ex 1766  df-nf 1770  df-sb 2045  df-mo 2578  df-eu 2614  df-clab 2778  df-cleq 2790  df-clel 2865  df-nfc 2937  df-ral 3112  df-rex 3113  df-rab 3116  df-v 3442  df-dif 3868  df-un 3870  df-in 3872  df-ss 3880  df-nul 4218  df-if 4388  df-pw 4461  df-sn 4479  df-pr 4481  df-op 4485  df-uni 4752  df-br 4969  df-opab 5031  df-xp 5456  df-rel 5457  df-cnv 5458  df-dm 5460  df-rn 5461  df-er 8146 This theorem is referenced by:  prtex  35568
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