Metamath Proof Explorer


Theorem nfel2

Description: Hypothesis builder for elementhood, special case. (Contributed by Mario Carneiro, 10-Oct-2016)

Ref Expression
Hypothesis nfeq2.1 _ x B
Assertion nfel2 x A B

Proof

Step Hyp Ref Expression
1 nfeq2.1 _ x B
2 nfcv _ x A
3 2 1 nfel x A B