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 e. _V
ceqsexv.2
|- ( x = A -> ( ph <-> ps ) )
Assertion ceqsexv
|- ( E. x ( x = A /\ ph ) <-> ps )

Proof

Step Hyp Ref Expression
1 ceqsexv.1
 |-  A e. _V
2 ceqsexv.2
 |-  ( x = A -> ( ph <-> ps ) )
3 alinexa
 |-  ( A. x ( x = A -> -. ph ) <-> -. E. x ( x = A /\ ph ) )
4 2 notbid
 |-  ( x = A -> ( -. ph <-> -. ps ) )
5 1 4 ceqsalv
 |-  ( A. x ( x = A -> -. ph ) <-> -. ps )
6 3 5 bitr3i
 |-  ( -. E. x ( x = A /\ ph ) <-> -. ps )
7 6 con4bii
 |-  ( E. x ( x = A /\ ph ) <-> ps )