Theorem cbvrexdvaOLD

Description: Obsolete version of cbvrexdva as of 9-Mar-2025. (Contributed by David Moews, 1-May-2017) (Proof modification is discouraged.) (New usage is discouraged.)

	Ref	Expression
Hypothesis	cbvrexdva.1	|- ( ( ph /\ x = y ) -> ( ps <-> ch ) )
Assertion	cbvrexdvaOLD	|- ( ph -> ( E. x e. A ps <-> E. y e. A ch ) )

Proof

Step	Hyp	Ref	Expression
1		cbvrexdva.1	|- ( ( ph /\ x = y ) -> ( ps <-> ch ) )
2		eqidd	|- ( ( ph /\ x = y ) -> A = A )
3	1 2	cbvrexdva2	|- ( ph -> ( E. x e. A ps <-> E. y e. A ch ) )