Metamath Proof Explorer


Theorem bnj946

Description: First-order logic and set theory. (Contributed by Jonathan Ben-Naim, 3-Jun-2011) (New usage is discouraged.)

Ref Expression
Hypothesis bnj946.1 φ x A ψ
Assertion bnj946 φ x x A ψ

Proof

Step Hyp Ref Expression
1 bnj946.1 φ x A ψ
2 df-ral x A ψ x x A ψ
3 1 2 bitri φ x x A ψ