Theorem orabs 900

Description: Absorption of redundant internal disjunct. Compare Theorem *4.45 of [WhiteheadRussell] p. 119. (Contributed by NM, 21-Jun-1993.) (Proof shortened by Wolf Lammen, 28-Feb-2014.)

Assertion

Ref	Expression
orabs	|- ( ph <-> ( ( ph \/ ps ) /\ ph ) )

Proof of Theorem orabs

Step	Hyp	Ref	Expression
1		orc 400	. 2 |- ( ph -> ( ph \/ ps ) )
2	1	pm4.71ri 665	1 |- ( ph <-> ( ( ph \/ ps ) /\ ph ) )

Syntax hints:   <-> wb 196   \/ wo 383   /\ wa 384

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 197  df-or 385  df-an 386

This theorem is referenced by: (None)