Theorem bitr3i

Description: An inference from transitive law for logical equivalence. (Contributed by NM, 2-Jun-1993)

	Ref	Expression
Hypotheses	bitr3i.1	|- ( ps <-> ph )
	bitr3i.2	|- ( ps <-> ch )
Assertion	bitr3i	|- ( ph <-> ch )

Proof

Step	Hyp	Ref	Expression
1		bitr3i.1	|- ( ps <-> ph )
2		bitr3i.2	|- ( ps <-> ch )
3	1	bicomi	|- ( ph <-> ps )
4	3 2	bitri	|- ( ph <-> ch )