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Theorem mth8 140
Description: Theorem 8 of [Margaris] p. 60. (Contributed by NM, 5-Aug-1993.) (Proof shortened by Josh Purinton, 29-Dec-2000.)
Assertion
Ref Expression
mth8  |-  ( ph  ->  ( -.  ps  ->  -.  ( ph  ->  ps ) ) )

Proof of Theorem mth8
StepHypRef Expression
1 pm2.27 37 . 2  |-  ( ph  ->  ( ( ph  ->  ps )  ->  ps )
)
21con3d 127 1  |-  ( ph  ->  ( -.  ps  ->  -.  ( ph  ->  ps ) ) )
Colors of variables: wff set class
Syntax hints:   -. wn 5    -> wi 6
This theorem is referenced by:  mont  24022  meran1  24024  onpsstopbas  24043
This theorem was proved from axioms:  ax-1 7  ax-2 8  ax-3 9  ax-mp 10
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