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Theorem pm4.55 481
Description: Theorem *4.55 of [WhiteheadRussell] p. 120. (Contributed by NM, 3-Jan-2005.)
Assertion
Ref Expression
pm4.55  |-  ( -.  ( -.  ph  /\  ps )  <->  ( ph  \/  -.  ps ) )

Proof of Theorem pm4.55
StepHypRef Expression
1 pm4.54 480 . . 3  |-  ( ( -.  ph  /\  ps )  <->  -.  ( ph  \/  -.  ps ) )
21con2bii 323 . 2  |-  ( (
ph  \/  -.  ps )  <->  -.  ( -.  ph  /\  ps ) )
32bicomi 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:  chrelat2i  23709  hlrelat2  29568
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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