Theorem vtoclgOLD

Description: Obsolete version of vtoclg as of 20-Apr-2024. (Contributed by NM, 17-Apr-1995) (New usage is discouraged.) (Proof modification is discouraged.)

	Ref	Expression
Hypotheses	vtoclgOLD.1	$$⊢x=A\to \left(\phi \leftrightarrow \psi \right)$$
	vtoclgOLD.2	$$⊢\phi$$
Assertion	vtoclgOLD	$$⊢A\in V\to \psi$$

Proof

Step	Hyp	Ref	Expression
1		vtoclgOLD.1	$$⊢x=A\to \left(\phi \leftrightarrow \psi \right)$$
2		vtoclgOLD.2	$$⊢\phi$$
3		nfv	$$⊢Ⅎx\psi$$
4	3 1 2	vtoclg1f	$$⊢A\in V\to \psi$$