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Theorem pm4.57 485
Description: Theorem *4.57 of [WhiteheadRussell] p. 120. (Contributed by NM, 3-Jan-2005.)
Assertion
Ref Expression
pm4.57  |-  ( -.  ( -.  ph  /\  -.  ps )  <->  ( ph  \/  ps ) )

Proof of Theorem pm4.57
StepHypRef Expression
1 oran 484 . 2  |-  ( (
ph  \/  ps )  <->  -.  ( -.  ph  /\  -.  ps ) )
21bicomi 195 1  |-  ( -.  ( -.  ph  /\  -.  ps )  <->  ( ph  \/  ps ) )
Colors of variables: wff set class
Syntax hints:   -. wn 5    <-> wb 178    \/ wo 359    /\ wa 360
This theorem is referenced by:  nanbi  1299  gcdaddmlem  12581  arg-ax  24029
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  df-or 361  df-an 362
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