Theorem 2albidv

Description: Formula-building rule for two universal quantifiers (deduction form). (Contributed by NM, 4-Mar-1997)

	Ref	Expression
Hypothesis	2albidv.1	|- ( ph -> ( ps <-> ch ) )
Assertion	2albidv	|- ( ph -> ( A. x A. y ps <-> A. x A. y ch ) )

Proof

Step	Hyp	Ref	Expression
1		2albidv.1	|- ( ph -> ( ps <-> ch ) )
2	1	albidv	|- ( ph -> ( A. y ps <-> A. y ch ) )
3	2	albidv	|- ( ph -> ( A. x A. y ps <-> A. x A. y ch ) )