Theorem rexbidvALT

Description: Alternate proof of rexbidv , shorter but requires more axioms. (Contributed by NM, 20-Nov-1994) (New usage is discouraged.) (Proof modification is discouraged.)

	Ref	Expression
Hypothesis	rexbidvALT.1	|- ( ph -> ( ps <-> ch ) )
Assertion	rexbidvALT	|- ( ph -> ( E. x e. A ps <-> E. x e. A ch ) )

Proof

Step	Hyp	Ref	Expression
1		rexbidvALT.1	|- ( ph -> ( ps <-> ch ) )
2		nfv	|- F/ x ph
3	2 1	rexbid	|- ( ph -> ( E. x e. A ps <-> E. x e. A ch ) )