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Theorem eqssi 3024
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  |-  A  C_  B
eqssi.2  |-  B  C_  A
Assertion
Ref Expression
eqssi  |-  A  =  B

Proof of Theorem eqssi
StepHypRef Expression
1 eqssi.1 . 2  |-  A  C_  B
2 eqssi.2 . 2  |-  B  C_  A
3 eqss 3023 . 2  |-  ( A  =  B  <->  ( A  C_  B  /\  B  C_  A ) )
41, 2, 3mpbir2an 884 1  |-  A  =  B
Colors of variables: wff set class
Syntax hints:    = wceq 1285    C_ wss 2982
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 1377  ax-7 1378  ax-gen 1379  ax-ie1 1423  ax-ie2 1424  ax-8 1436  ax-11 1438  ax-4 1441  ax-17 1460  ax-i9 1464  ax-ial 1468  ax-i5r 1469  ax-ext 2065
This theorem depends on definitions:  df-bi 115  df-nf 1391  df-sb 1688  df-clab 2070  df-cleq 2076  df-clel 2079  df-in 2988  df-ss 2995
This theorem is referenced by:  inv1  3296  unv  3297  undifabs  3336  intab  3685  intid  4007  find  4368  limom  4382  dmv  4599  0ima  4735  rnxpid  4805  dftpos4  5932  djuun  6558  dfuzi  8590  unirnioo  9124
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