Theorem nfn

Description: Inference associated with nfnt . (Contributed by Mario Carneiro, 11-Aug-2016) df-nf changed. (Revised by Wolf Lammen, 18-Sep-2021)

	Ref	Expression
Hypothesis	nfn.1	|- F/ x ph
Assertion	nfn	|- F/ x -. ph

Proof

Step	Hyp	Ref	Expression
1		nfn.1	|- F/ x ph
2		nfnt	|- ( F/ x ph -> F/ x -. ph )
3	1 2	ax-mp	|- F/ x -. ph