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Theorem eqssi 3039
Description: Infer equality from two subclass relationships. Compare Theorem 4 of [Suppes] p. 22. (Contributed by NM, 9-Sep-1993.)
Hypotheses
Ref Expression
eqssi.1 𝐴𝐵
eqssi.2 𝐵𝐴
Assertion
Ref Expression
eqssi 𝐴 = 𝐵

Proof of Theorem eqssi
StepHypRef Expression
1 eqssi.1 . 2 𝐴𝐵
2 eqssi.2 . 2 𝐵𝐴
3 eqss 3038 . 2 (𝐴 = 𝐵 ↔ (𝐴𝐵𝐵𝐴))
41, 2, 3mpbir2an 888 1 𝐴 = 𝐵
Colors of variables: wff set class
Syntax hints:   = wceq 1289  wss 2997
This theorem was proved from axioms:  ax-1 5  ax-2 6  ax-mp 7  ax-ia1 104  ax-ia2 105  ax-ia3 106  ax-5 1381  ax-7 1382  ax-gen 1383  ax-ie1 1427  ax-ie2 1428  ax-8 1440  ax-11 1442  ax-4 1445  ax-17 1464  ax-i9 1468  ax-ial 1472  ax-i5r 1473  ax-ext 2070
This theorem depends on definitions:  df-bi 115  df-nf 1395  df-sb 1693  df-clab 2075  df-cleq 2081  df-clel 2084  df-in 3003  df-ss 3010
This theorem is referenced by:  inv1  3316  unv  3317  undifabs  3356  intab  3712  intid  4042  find  4404  limom  4418  dmv  4640  0ima  4779  rnxpid  4852  dftpos4  6010  djuun  6739  dfuzi  8826  unirnioo  9360
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