Theorem nfcvf2

Description: If x and y are distinct, then y is not free in x . Usage of this theorem is discouraged because it depends on ax-13 . See nfcv for a version that replaces the distinctor with a disjoint variable condition, requiring fewer axioms. (Contributed by Mario Carneiro, 5-Dec-2016) (New usage is discouraged.)

	Ref	Expression
Assertion	nfcvf2	|- ( -. A. x x = y -> F/_ y x )

Proof

Step	Hyp	Ref	Expression
1		nfcvf	|- ( -. A. y y = x -> F/_ y x )
2	1	naecoms	|- ( -. A. x x = y -> F/_ y x )