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Theorem pm5.5 240
Description: Theorem *5.5 of [WhiteheadRussell] p. 125. (Contributed by NM, 3-Jan-2005.)
Assertion
Ref Expression
pm5.5  |-  ( ph  ->  ( ( ph  ->  ps )  <->  ps ) )

Proof of Theorem pm5.5
StepHypRef Expression
1 biimt 239 . 2  |-  ( ph  ->  ( ps  <->  ( ph  ->  ps ) ) )
21bicomd 139 1  |-  ( ph  ->  ( ( ph  ->  ps )  <->  ps ) )
Colors of variables: wff set class
Syntax hints:    -> wi 4    <-> wb 103
This theorem was proved from axioms:  ax-1 5  ax-2 6  ax-mp 7  ax-ia1 104  ax-ia2 105  ax-ia3 106
This theorem depends on definitions:  df-bi 115
This theorem is referenced by:  imim21b  250  elabgt  2736  sbceqal  2870  dffun8  4953  ordiso2  6495  indstr2  8766  dfgcd2  10536
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