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 𝐴𝐵

Proof

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