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Theorem risset 2438
Description: Two ways to say " A belongs to  B." (Contributed by NM, 22-Nov-1994.)
Assertion
Ref Expression
risset  |-  ( A  e.  B  <->  E. x  e.  B  x  =  A )
Distinct variable groups:    x, A    x, B

Proof of Theorem risset
StepHypRef Expression
1 exancom 1570 . 2  |-  ( E. x ( x  e.  B  /\  x  =  A )  <->  E. x
( x  =  A  /\  x  e.  B
) )
2 df-rex 2397 . 2  |-  ( E. x  e.  B  x  =  A  <->  E. x
( x  e.  B  /\  x  =  A
) )
3 df-clel 2111 . 2  |-  ( A  e.  B  <->  E. x
( x  =  A  /\  x  e.  B
) )
41, 2, 33bitr4ri 212 1  |-  ( A  e.  B  <->  E. x  e.  B  x  =  A )
Colors of variables: wff set class
Syntax hints:    /\ wa 103    <-> wb 104    = wceq 1314   E.wex 1451    e. wcel 1463   E.wrex 2392
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-5 1406  ax-gen 1408  ax-ie1 1452  ax-ie2 1453  ax-4 1470  ax-ial 1497
This theorem depends on definitions:  df-bi 116  df-clel 2111  df-rex 2397
This theorem is referenced by:  reueq  2854  reuind  2860  0el  3353  iunid  3836  sucel  4300  reusv3  4349  fvmptt  5478  releldm2  6049  qsid  6460  rerecclap  8450  nndiv  8718  zq  9367  4fvwrd4  9857  bj-bdcel  12846
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