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Theorem orabs 828
Description: Absorption of redundant internal disjunct. Compare Theorem *4.45 of [WhiteheadRussell] p. 119. (Contributed by NM, 5-Aug-1993.) (Proof shortened by Wolf Lammen, 28-Feb-2014.)
Assertion
Ref Expression
orabs  |-  ( ph  <->  ( ( ph  \/  ps )  /\  ph ) )

Proof of Theorem orabs
StepHypRef Expression
1 orc 374 . 2  |-  ( ph  ->  ( ph  \/  ps ) )
21pm4.71ri 614 1  |-  ( ph  <->  ( ( ph  \/  ps )  /\  ph ) )
Colors of variables: wff set class
Syntax hints:    <-> wb 176    \/ wo 357    /\ wa 358
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  df-an 360
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