Theorem 2thALT

Description: Alternate proof of 2th . (Contributed by Hongxiu Chen, 29-Jun-2025) (Proof modification is discouraged.) (New usage is discouraged.)

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

Proof

Step	Hyp	Ref	Expression
1		2thALT.1	|- ph
2		2thALT.2	|- ps
3		pm5.1im	|- ( ph -> ( ps -> ( ph <-> ps ) ) )
4	1 2 3	mp2	|- ( ph <-> ps )