Theorem bj-nfdt0

Description: A theorem close to a closed form of nf5d and nf5dh . (Contributed by BJ, 2-May-2019)

	Ref	Expression
Assertion	bj-nfdt0	|- ( A. x ( ph -> ( ps -> A. x ps ) ) -> ( A. x ph -> F/ x ps ) )

Proof

Step	Hyp	Ref	Expression
1		alim	|- ( A. x ( ph -> ( ps -> A. x ps ) ) -> ( A. x ph -> A. x ( ps -> A. x ps ) ) )
2		nf5	|- ( F/ x ps <-> A. x ( ps -> A. x ps ) )
3	1 2	imbitrrdi	|- ( A. x ( ph -> ( ps -> A. x ps ) ) -> ( A. x ph -> F/ x ps ) )