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Theorem pm2.51 147
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 7 . . 3  |-  ( ps 
->  ( ph  ->  ps ) )
21con3i 129 . 2  |-  ( -.  ( ph  ->  ps )  ->  -.  ps )
32a1d 24 1  |-  ( -.  ( ph  ->  ps )  ->  ( ph  ->  -. 
ps ) )
Colors of variables: wff set class
Syntax hints:   -. wn 5    -> wi 6
This theorem is referenced by:  pm5.12  860
This theorem was proved from axioms:  ax-1 7  ax-2 8  ax-3 9  ax-mp 10
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