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Theorem pm4.25 501
Description: Theorem *4.25 of [WhiteheadRussell] p. 117. (Contributed by NM, 3-Jan-2005.)
Assertion
Ref Expression
pm4.25  |-  ( ph  <->  (
ph  \/  ph ) )

Proof of Theorem pm4.25
StepHypRef Expression
1 oridm 500 . 2  |-  ( (
ph  \/  ph )  <->  ph )
21bicomi 193 1  |-  ( ph  <->  (
ph  \/  ph ) )
Colors of variables: wff set class
Syntax hints:    <-> wb 176    \/ wo 357
This theorem is referenced by:  brbtwn2  24533  srefwref  25067
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 177  df-or 359
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