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Theorem pm4.56 482
Description: Theorem *4.56 of [WhiteheadRussell] p. 120. (Contributed by NM, 3-Jan-2005.)
Assertion
Ref Expression
pm4.56  |-  ( ( -.  ph  /\  -.  ps ) 
<->  -.  ( ph  \/  ps ) )

Proof of Theorem pm4.56
StepHypRef Expression
1 ioran 477 . 2  |-  ( -.  ( ph  \/  ps ) 
<->  ( -.  ph  /\  -.  ps ) )
21bicomi 194 1  |-  ( ( -.  ph  /\  -.  ps ) 
<->  -.  ( ph  \/  ps ) )
Colors of variables: wff set class
Syntax hints:   -. wn 3    <-> wb 177    \/ wo 358    /\ wa 359
This theorem is referenced by:  oran  483  neanior  2683  prneimg  3970  ordtri3  4609  ssxr  9134  isirred2  15794  aaliou3lem9  20255  jm2.26lem3  27009  wopprc  27038  iunconlem2  28902  dalawlem13  30519  cdleme22b  30977
This theorem was proved from axioms:  ax-1 5  ax-2 6  ax-3 7  ax-mp 8
This theorem depends on definitions:  df-bi 178  df-or 360  df-an 361
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