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Theorem con2 116
Description: Contraposition. Theorem *2.03 of [WhiteheadRussell] p. 100. (Contributed by NM, 29-Dec-1992.) (Proof shortened by Wolf Lammen, 12-Feb-2013.)
Assertion
Ref Expression
con2  |-  ( (
ph  ->  -.  ps )  ->  ( ps  ->  -.  ph ) )

Proof of Theorem con2
StepHypRef Expression
1 id 22 . 2  |-  ( (
ph  ->  -.  ps )  ->  ( ph  ->  -.  ps ) )
21con2d 115 1  |-  ( (
ph  ->  -.  ps )  ->  ( ps  ->  -.  ph ) )
Colors of variables: wff setvar class
Syntax hints:   -. wn 3    -> wi 4
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8
This theorem is referenced by:  con2b  334  isprm5  14356  bj-con2com  34325  bj-axtd  34368
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