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Theorem eluni2 3800
Description: Membership in class union. Restricted quantifier version. (Contributed by NM, 31-Aug-1999.)
Assertion
Ref Expression
eluni2  |-  ( A  e.  U. B  <->  E. x  e.  B  A  e.  x )
Distinct variable groups:    x, A    x, B

Proof of Theorem eluni2
StepHypRef Expression
1 exancom 1601 . 2  |-  ( E. x ( A  e.  x  /\  x  e.  B )  <->  E. x
( x  e.  B  /\  A  e.  x
) )
2 eluni 3799 . 2  |-  ( A  e.  U. B  <->  E. x
( A  e.  x  /\  x  e.  B
) )
3 df-rex 2454 . 2  |-  ( E. x  e.  B  A  e.  x  <->  E. x ( x  e.  B  /\  A  e.  x ) )
41, 2, 33bitr4i 211 1  |-  ( A  e.  U. B  <->  E. x  e.  B  A  e.  x )
Colors of variables: wff set class
Syntax hints:    /\ wa 103    <-> wb 104   E.wex 1485    e. wcel 2141   E.wrex 2449   U.cuni 3796
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-ia1 105  ax-ia2 106  ax-ia3 107  ax-io 704  ax-5 1440  ax-7 1441  ax-gen 1442  ax-ie1 1486  ax-ie2 1487  ax-8 1497  ax-10 1498  ax-11 1499  ax-i12 1500  ax-bndl 1502  ax-4 1503  ax-17 1519  ax-i9 1523  ax-ial 1527  ax-i5r 1528  ax-ext 2152
This theorem depends on definitions:  df-bi 116  df-tru 1351  df-nf 1454  df-sb 1756  df-clab 2157  df-cleq 2163  df-clel 2166  df-nfc 2301  df-rex 2454  df-v 2732  df-uni 3797
This theorem is referenced by:  uni0b  3821  intssunim  3853  iuncom4  3880  inuni  4141  ssorduni  4471  unon  4495  cnvuni  4797  chfnrn  5607  isbasis3g  12838  eltg2b  12848  tgcl  12858  epttop  12884  txuni2  13050
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