Description: Equality deduction for restricted universal quantifier. (Contributed by NM, 6-Nov-2007) Remove usage of ax-10 , ax-11 , and ax-12 and reduce distinct variable conditions. (Revised by Steven Nguyen, 30-Apr-2023)
|- ( ph -> A = B )
|- ( ph -> ( ps <-> ch ) )
|- ( ph -> ( A. x e. A ps <-> A. x e. B ch ) )
|- ( ph -> ( x e. A <-> x e. B ) )
|- ( ph -> ( ( x e. A -> ps ) <-> ( x e. B -> ch ) ) )