Theorem nfxfrdOLD 1838

Description: Obsolete proof of nfxfrd 1780 as of 6-Oct-2021. (Contributed by Mario Carneiro, 24-Sep-2016.) (Proof modification is discouraged.) (New usage is discouraged.)

Hypotheses

Ref	Expression
nfbiiOLD.1	|- ( ph <-> ps )
nfxfrdOLD.2	|- ( ch -> F/ x ps )

Assertion

Ref	Expression
nfxfrdOLD	|- ( ch -> F/ x ph )

Proof of Theorem nfxfrdOLD

Step	Hyp	Ref	Expression
1		nfxfrdOLD.2	. 2 |- ( ch -> F/ x ps )
2		nfbiiOLD.1	. . 3 |- ( ph <-> ps )
3	2	nfbiiOLD 1836	. 2 |- ( F/ x ph <-> F/ x ps )
4	1, 3	sylibr 224	1 |- ( ch -> F/ x ph )

Syntax hints:   -> wi 4   <-> wb 196   F/wnfOLD 1709

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1722  ax-4 1737

This theorem depends on definitions:  df-bi 197  df-nfOLD 1721

This theorem is referenced by:  nfandOLD  2232  nf3andOLD  2233  nfbidOLD  2242