Theorem albii

Description: Inference adding universal quantifier to both sides of an equivalence. (Contributed by NM, 7-Aug-1994)

	Ref	Expression
Hypothesis	albii.1	|- ( ph <-> ps )
Assertion	albii	|- ( A. x ph <-> A. x ps )

Proof

Step	Hyp	Ref	Expression
1		albii.1	|- ( ph <-> ps )
2		albi	|- ( A. x ( ph <-> ps ) -> ( A. x ph <-> A. x ps ) )
3	2 1	mpg	|- ( A. x ph <-> A. x ps )