Metamath Proof Explorer


Theorem nfcvd

Description: If x is disjoint from A , then x is not free in A . (Contributed by Mario Carneiro, 7-Oct-2016)

Ref Expression
Assertion nfcvd φ _ x A

Proof

Step Hyp Ref Expression
1 nfcv _ x A
2 1 a1i φ _ x A