Theorem dfvd2impr

Description: A 2-antecedent nested implication implies its virtual deduction form. (Contributed by Alan Sare, 21-Apr-2011) (Proof modification is discouraged.) (New usage is discouraged.)

	Ref	Expression
Assertion	dfvd2impr	|- ( ( ph -> ( ps -> ch ) ) -> (. ph ,. ps ->. ch ). )

Proof

Step	Hyp	Ref	Expression
1		dfvd2	|- ( (. ph ,. ps ->. ch ). <-> ( ph -> ( ps -> ch ) ) )
2	1	biimpri	|- ( ( ph -> ( ps -> ch ) ) -> (. ph ,. ps ->. ch ). )