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Theorem pm5.41 355
Description: Theorem *5.41 of [WhiteheadRussell] p. 125. (Contributed by NM, 3-Jan-2005.) (Proof shortened by Wolf Lammen, 12-Oct-2012.)
Assertion
Ref Expression
pm5.41  |-  ( ( ( ph  ->  ps )  ->  ( ph  ->  ch ) )  <->  ( ph  ->  ( ps  ->  ch ) ) )

Proof of Theorem pm5.41
StepHypRef Expression
1 imdi 354 . 2  |-  ( (
ph  ->  ( ps  ->  ch ) )  <->  ( ( ph  ->  ps )  -> 
( ph  ->  ch )
) )
21bicomi 195 1  |-  ( ( ( ph  ->  ps )  ->  ( ph  ->  ch ) )  <->  ( ph  ->  ( ps  ->  ch ) ) )
Colors of variables: wff set class
Syntax hints:    -> wi 6    <-> wb 178
This theorem was proved from axioms:  ax-1 7  ax-2 8  ax-3 9  ax-mp 10
This theorem depends on definitions:  df-bi 179
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