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Theorem dfss 3260
Description: Variant of subclass definition df-ss 3259. (Contributed by NM, 3-Sep-2004.)
Assertion
Ref Expression
dfss (A BA = (AB))

Proof of Theorem dfss
StepHypRef Expression
1 df-ss 3259 . 2 (A B ↔ (AB) = A)
2 eqcom 2355 . 2 ((AB) = AA = (AB))
31, 2bitri 240 1 (A BA = (AB))
Colors of variables: wff setvar class
Syntax hints:  wb 176   = wceq 1642  cin 3208   wss 3257
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1546  ax-5 1557  ax-ext 2334
This theorem depends on definitions:  df-bi 177  df-cleq 2346  df-ss 3259
This theorem is referenced by:  dfss2  3262  iinrab2  4029  funimass1  5169
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