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Theorem pm4.25 503
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 502 . 2  |-  ( (
ph  \/  ph )  <->  ph )
21bicomi 195 1  |-  ( ph  <->  (
ph  \/  ph ) )
Colors of variables: wff set class
Syntax hints:    <-> wb 178    \/ wo 359
This theorem is referenced by:  brbtwn2  23940  srefwref  24465
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
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