Metamath Proof Explorer


Theorem ceqsexv

Description: Elimination of an existential quantifier, using implicit substitution. (Contributed by NM, 2-Mar-1995) Avoid ax-12 . (Revised by Gino Giotto, 12-Oct-2024) (Proof shortened by Wolf Lammen, 22-Jan-2025)

Ref Expression
Hypotheses ceqsexv.1 A V
ceqsexv.2 x = A φ ψ
Assertion ceqsexv x x = A φ ψ

Proof

Step Hyp Ref Expression
1 ceqsexv.1 A V
2 ceqsexv.2 x = A φ ψ
3 alinexa x x = A ¬ φ ¬ x x = A φ
4 2 notbid x = A ¬ φ ¬ ψ
5 1 4 ceqsalv x x = A ¬ φ ¬ ψ
6 3 5 bitr3i ¬ x x = A φ ¬ ψ
7 6 con4bii x x = A φ ψ