Theorem dfvd1impr

Description: Right-to-left part of definition of virtual deduction. (Contributed by Alan Sare, 21-Apr-2011) (Proof modification is discouraged.) (New usage is discouraged.)

	Ref	Expression
Assertion	dfvd1impr	|- ( ( ph -> ps ) -> (. ph ->. ps ). )

Proof

Step	Hyp	Ref	Expression
1		df-vd1	|- ( (. ph ->. ps ). <-> ( ph -> ps ) )
2	1	biimpri	|- ( ( ph -> ps ) -> (. ph ->. ps ). )