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Theorem eluni2 3708
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 1570 . 2  |-  ( E. x ( A  e.  x  /\  x  e.  B )  <->  E. x
( x  e.  B  /\  A  e.  x
) )
2 eluni 3707 . 2  |-  ( A  e.  U. B  <->  E. x
( A  e.  x  /\  x  e.  B
) )
3 df-rex 2397 . 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 1451    e. wcel 1463   E.wrex 2392   U.cuni 3704
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 681  ax-5 1406  ax-7 1407  ax-gen 1408  ax-ie1 1452  ax-ie2 1453  ax-8 1465  ax-10 1466  ax-11 1467  ax-i12 1468  ax-bndl 1469  ax-4 1470  ax-17 1489  ax-i9 1493  ax-ial 1497  ax-i5r 1498  ax-ext 2097
This theorem depends on definitions:  df-bi 116  df-tru 1317  df-nf 1420  df-sb 1719  df-clab 2102  df-cleq 2108  df-clel 2111  df-nfc 2245  df-rex 2397  df-v 2660  df-uni 3705
This theorem is referenced by:  uni0b  3729  intssunim  3761  iuncom4  3788  inuni  4048  ssorduni  4371  unon  4395  cnvuni  4693  chfnrn  5497  isbasis3g  12108  eltg2b  12118  tgcl  12128  epttop  12154  txuni2  12320
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