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Theorem eldifbd 3178
Description: If a class is in the difference of two classes, it is not in the subtrahend. One-way deduction form of eldif 3175. (Contributed by David Moews, 1-May-2017.)
Hypothesis
Ref Expression
eldifbd.1  |-  ( ph  ->  A  e.  ( B 
\  C ) )
Assertion
Ref Expression
eldifbd  |-  ( ph  ->  -.  A  e.  C
)

Proof of Theorem eldifbd
StepHypRef Expression
1 eldifbd.1 . . 3  |-  ( ph  ->  A  e.  ( B 
\  C ) )
2 eldif 3175 . . 3  |-  ( A  e.  ( B  \  C )  <->  ( A  e.  B  /\  -.  A  e.  C ) )
31, 2sylib 188 . 2  |-  ( ph  ->  ( A  e.  B  /\  -.  A  e.  C
) )
43simprd 449 1  |-  ( ph  ->  -.  A  e.  C
)
Colors of variables: wff set class
Syntax hints:   -. wn 3    -> wi 4    /\ wa 358    e. wcel 1696    \ cdif 3162
This theorem was proved from axioms:  ax-1 5  ax-2 6  ax-3 7  ax-mp 8  ax-gen 1536  ax-5 1547  ax-17 1606  ax-9 1644  ax-8 1661  ax-6 1715  ax-7 1720  ax-11 1727  ax-12 1878  ax-ext 2277
This theorem depends on definitions:  df-bi 177  df-or 359  df-an 360  df-tru 1310  df-ex 1532  df-nf 1535  df-sb 1639  df-clab 2283  df-cleq 2289  df-clel 2292  df-nfc 2421  df-v 2803  df-dif 3168
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