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Theorem dfss 2909
Description: Variant of subclass definition df-ss 2908. (Contributed by NM, 3-Sep-2004.)
Assertion
Ref Expression
dfss (ABA = (AB))

Proof of Theorem dfss
StepHypRef Expression
1 df-ss 2908 . 2 (AB ↔ (AB) = A)
2 eqcom 2024 . 2 ((AB) = AA = (AB))
31, 2bitri 173 1 (ABA = (AB))
Colors of variables: wff set class
Syntax hints:  wb 98   = wceq 1228  cin 2893  wss 2894
This theorem was proved from axioms:  ax-1 5  ax-2 6  ax-mp 7  ax-ia1 99  ax-ia2 100  ax-ia3 101  ax-5 1316  ax-gen 1318  ax-ext 2004
This theorem depends on definitions:  df-bi 110  df-cleq 2015  df-ss 2908
This theorem is referenced by:  dfss2  2911  onelini  4117  cnvcnv  4700  funimass1  4902  dmaddpi  6185  dmmulpi  6186
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