Theorem bicomi

Description: Inference from commutative law for logical equivalence. (Contributed by NM, 3-Jan-1993)

	Ref	Expression
Hypothesis	bicomi.1	|- ( ph <-> ps )
Assertion	bicomi	|- ( ps <-> ph )

Proof

Step	Hyp	Ref	Expression
1		bicomi.1	|- ( ph <-> ps )
2		bicom1	|- ( ( ph <-> ps ) -> ( ps <-> ph ) )
3	1 2	ax-mp	|- ( ps <-> ph )