Theorem orabs 809

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

Step	Hyp	Ref	Expression
1		orc 707	. 2 |- ( ph -> ( ph \/ ps ) )
2	1	pm4.71ri 390	1 |- ( ph <-> ( ( ph \/ ps ) /\ ph ) )

Syntax hints:   /\ wa 103   <-> wb 104   \/ wo 703

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-ia1 105  ax-ia2 106  ax-ia3 107  ax-io 704

This theorem depends on definitions:  df-bi 116

This theorem is referenced by: (None)