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Theorem erdm 6544
Description: The domain of an equivalence relation. (Contributed by Mario Carneiro, 12-Aug-2015.)
Assertion
Ref Expression
erdm (𝑅 Er 𝐴 → dom 𝑅 = 𝐴)

Proof of Theorem erdm
StepHypRef Expression
1 df-er 6534 . 2 (𝑅 Er 𝐴 ↔ (Rel 𝑅 ∧ dom 𝑅 = 𝐴 ∧ (𝑅 ∪ (𝑅𝑅)) ⊆ 𝑅))
21simp2bi 1013 1 (𝑅 Er 𝐴 → dom 𝑅 = 𝐴)
Colors of variables: wff set class
Syntax hints:  wi 4   = wceq 1353  cun 3127  wss 3129  ccnv 4625  dom cdm 4626  ccom 4630  Rel wrel 4631   Er wer 6531
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-ia1 106  ax-ia2 107
This theorem depends on definitions:  df-bi 117  df-3an 980  df-er 6534
This theorem is referenced by:  ercl  6545  erref  6554  errn  6556  erssxp  6557  erexb  6559  ereldm  6577  uniqs2  6594  iinerm  6606  th3qlem1  6636  0nnq  7362  nnnq0lem1  7444  prsrlem1  7740  gt0srpr  7746  0nsr  7747
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