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Theorem pm2.51 145
Description: Theorem *2.51 of [WhiteheadRussell] p. 107. (Contributed by NM, 3-Jan-2005.)
Assertion
Ref Expression
pm2.51  |-  ( -.  ( ph  ->  ps )  ->  ( ph  ->  -. 
ps ) )

Proof of Theorem pm2.51
StepHypRef Expression
1 ax-1 5 . . 3  |-  ( ps 
->  ( ph  ->  ps ) )
21con3i 127 . 2  |-  ( -.  ( ph  ->  ps )  ->  -.  ps )
32a1d 22 1  |-  ( -.  ( ph  ->  ps )  ->  ( ph  ->  -. 
ps ) )
Colors of variables: wff set class
Syntax hints:   -. wn 3    -> wi 4
This theorem is referenced by:  pm5.12  855
This theorem was proved from axioms:  ax-1 5  ax-2 6  ax-3 7  ax-mp 8
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