Theorem bi2imp

Description: Importation inference similar to imp , except both implications of the hypothesis are biconditionals. (Contributed by Alan Sare, 6-Nov-2017)

	Ref	Expression
Hypothesis	bi2imp.1	|- ( ph <-> ( ps <-> ch ) )
Assertion	bi2imp	|- ( ( ph /\ ps ) -> ch )

Proof

Step	Hyp	Ref	Expression
1		bi2imp.1	|- ( ph <-> ( ps <-> ch ) )
2	1	biimpi	|- ( ph -> ( ps <-> ch ) )
3	2	biimpa	|- ( ( ph /\ ps ) -> ch )