Theorem elabOLD

Description: Obsolete version of elab as of 5-Oct-2024. (Contributed by NM, 1-Aug-1994) (Proof modification is discouraged.) (New usage is discouraged.)

	Ref	Expression
Hypotheses	elab.1	|- A e. _V
	elab.2	|- ( x = A -> ( ph <-> ps ) )
Assertion	elabOLD	|- ( A e. { x | ph } <-> ps )

Proof

Step	Hyp	Ref	Expression
1		elab.1	|- A e. _V
2		elab.2	|- ( x = A -> ( ph <-> ps ) )
3		nfv	|- F/ x ps
4	3 1 2	elabf	|- ( A e. { x | ph } <-> ps )