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Theorem pm4.66 422
Description: Theorem *4.66 of [WhiteheadRussell] p. 120. (Contributed by NM, 3-Jan-2005.)
Assertion
Ref Expression
pm4.66  |-  ( ( -.  ph  ->  -.  ps ) 
<->  ( ph  \/  -.  ps ) )

Proof of Theorem pm4.66
StepHypRef Expression
1 pm4.64 374 1  |-  ( ( -.  ph  ->  -.  ps ) 
<->  ( ph  \/  -.  ps ) )
Colors of variables: wff setvar class
Syntax hints:   -. wn 3    -> wi 4    <-> wb 188    \/ wo 370
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8
This theorem depends on definitions:  df-bi 189  df-or 372
This theorem is referenced by:  pm4.54  496  ifpim123g  36070  hirstL-ax3  38198
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