Theorem bianabs

Description: Absorb a hypothesis into the second member of a biconditional. (Contributed by FL, 15-Feb-2007)

	Ref	Expression
Hypothesis	bianabs.1	|- ( ph -> ( ps <-> ( ph /\ ch ) ) )
Assertion	bianabs	|- ( ph -> ( ps <-> ch ) )

Proof

Step	Hyp	Ref	Expression
1		bianabs.1	|- ( ph -> ( ps <-> ( ph /\ ch ) ) )
2		ibar	|- ( ph -> ( ch <-> ( ph /\ ch ) ) )
3	1 2	bitr4d	|- ( ph -> ( ps <-> ch ) )