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Theorem eldifsn 3519
Description: Membership in a set with an element removed. (Contributed by NM, 10-Oct-2007.)
Assertion
Ref Expression
eldifsn  |-  ( A  e.  ( B  \  { C } )  <->  ( A  e.  B  /\  A  =/= 
C ) )

Proof of Theorem eldifsn
StepHypRef Expression
1 eldif 2983 . 2  |-  ( A  e.  ( B  \  { C } )  <->  ( A  e.  B  /\  -.  A  e.  { C } ) )
2 elsng 3415 . . . 4  |-  ( A  e.  B  ->  ( A  e.  { C } 
<->  A  =  C ) )
32necon3bbid 2286 . . 3  |-  ( A  e.  B  ->  ( -.  A  e.  { C } 
<->  A  =/=  C ) )
43pm5.32i 442 . 2  |-  ( ( A  e.  B  /\  -.  A  e.  { C } )  <->  ( A  e.  B  /\  A  =/= 
C ) )
51, 4bitri 182 1  |-  ( A  e.  ( B  \  { C } )  <->  ( A  e.  B  /\  A  =/= 
C ) )
Colors of variables: wff set class
Syntax hints:   -. wn 3    /\ wa 102    <-> wb 103    e. wcel 1434    =/= wne 2246    \ cdif 2971   {csn 3400
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-in1 577  ax-in2 578  ax-io 663  ax-5 1377  ax-7 1378  ax-gen 1379  ax-ie1 1423  ax-ie2 1424  ax-8 1436  ax-10 1437  ax-11 1438  ax-i12 1439  ax-bndl 1440  ax-4 1441  ax-17 1460  ax-i9 1464  ax-ial 1468  ax-i5r 1469  ax-ext 2064
This theorem depends on definitions:  df-bi 115  df-tru 1288  df-nf 1391  df-sb 1687  df-clab 2069  df-cleq 2075  df-clel 2078  df-nfc 2209  df-ne 2247  df-v 2604  df-dif 2976  df-sn 3406
This theorem is referenced by:  eldifsni  3520  rexdifsn  3523  difsn  3525  fnniniseg2  5316  rexsupp  5317  suppssfv  5733  suppssov1  5734  dif1o  6079  fidifsnen  6395  en2eleq  6511  en2other2  6512  elni  6549  divvalap  7818  elnnne0  8358  divfnzn  8776  modfzo0difsn  9466  modsumfzodifsn  9467  fzo0dvdseq  10391  oddprmgt2  10648
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