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Theorem eldifad 2985
Description: If a class is in the difference of two classes, it is also in the minuend. One-way deduction form of eldif 2983. (Contributed by David Moews, 1-May-2017.)
Hypothesis
Ref Expression
eldifad.1  |-  ( ph  ->  A  e.  ( B 
\  C ) )
Assertion
Ref Expression
eldifad  |-  ( ph  ->  A  e.  B )

Proof of Theorem eldifad
StepHypRef Expression
1 eldifad.1 . . 3  |-  ( ph  ->  A  e.  ( B 
\  C ) )
2 eldif 2983 . . 3  |-  ( A  e.  ( B  \  C )  <->  ( A  e.  B  /\  -.  A  e.  C ) )
31, 2sylib 120 . 2  |-  ( ph  ->  ( A  e.  B  /\  -.  A  e.  C
) )
43simpld 110 1  |-  ( ph  ->  A  e.  B )
Colors of variables: wff set class
Syntax hints:   -. wn 3    -> wi 4    /\ wa 102    e. wcel 1434    \ cdif 2971
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-v 2604  df-dif 2976
This theorem is referenced by:  unfidisj  6432  undiffi  6433  fnfi  6436  sizeunlem  9817
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