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Theorem pm4.56 495
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 490 . 2  |-  ( -.  ( ph  \/  ps ) 
<->  ( -.  ph  /\  -.  ps ) )
21bicomi 202 1  |-  ( ( -.  ph  /\  -.  ps ) 
<->  -.  ( ph  \/  ps ) )
Colors of variables: wff setvar class
Syntax hints:   -. wn 3    <-> wb 184    \/ wo 368    /\ wa 369
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 185  df-or 370  df-an 371
This theorem is referenced by:  oran  496  neanior  2777  prneimg  4162  ordtri3  4864  ssxr  9556  isirred2  16917  aaliou3lem9  21950  coltr2  23193  mideulem  23262  jm2.26lem3  29499  wopprc  29528  islininds2  31151  iunconlem2  32004  bj-dfbi4  32410  dalawlem13  33866  cdleme22b  34324
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