Theorem bitr2d

Description: Deduction form of bitr2i . (Contributed by NM, 9-Jun-2004)

	Ref	Expression
Hypotheses	bitr2d.1	|- ( ph -> ( ps <-> ch ) )
	bitr2d.2	|- ( ph -> ( ch <-> th ) )
Assertion	bitr2d	|- ( ph -> ( th <-> ps ) )

Proof

Step	Hyp	Ref	Expression
1		bitr2d.1	|- ( ph -> ( ps <-> ch ) )
2		bitr2d.2	|- ( ph -> ( ch <-> th ) )
3	1 2	bitrd	|- ( ph -> ( ps <-> th ) )
4	3	bicomd	|- ( ph -> ( th <-> ps ) )