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Metamath Proof Explorer

Theorem nfel1

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

Ref Expression
Hypothesis nfeq1.1 ⊢ Ⅎ _ x A
Assertion nfel1 ⊢ Ⅎ x A ∈ B

Proof

Step Hyp Ref Expression
1 nfeq1.1 ⊢ Ⅎ _ x A
2 nfcv ⊢ Ⅎ _ x B
3 1 2 nfel ⊢ Ⅎ x A ∈ B