Theorem bitr3d

Description: Deduction form of bitr3i . (Contributed by NM, 14-May-1993)

	Ref	Expression
Hypotheses	bitr3d.1	|- ( ph -> ( ps <-> ch ) )
	bitr3d.2	|- ( ph -> ( ps <-> th ) )
Assertion	bitr3d	|- ( ph -> ( ch <-> th ) )

Proof

Step	Hyp	Ref	Expression
1		bitr3d.1	|- ( ph -> ( ps <-> ch ) )
2		bitr3d.2	|- ( ph -> ( ps <-> th ) )
3	1	bicomd	|- ( ph -> ( ch <-> ps ) )
4	3 2	bitrd	|- ( ph -> ( ch <-> th ) )