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Theorem pm5.41 250
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 249 . 2  |-  ( (
ph  ->  ( ps  ->  ch ) )  <->  ( ( ph  ->  ps )  -> 
( ph  ->  ch )
) )
21bicomi 131 1  |-  ( ( ( ph  ->  ps )  ->  ( ph  ->  ch ) )  <->  ( ph  ->  ( ps  ->  ch ) ) )
Colors of variables: wff set class
Syntax hints:    -> wi 4    <-> wb 104
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-ia1 105  ax-ia2 106  ax-ia3 107
This theorem depends on definitions:  df-bi 116
This theorem is referenced by: (None)
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