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	⊢ 𝜑
	2thALT.2	⊢ 𝜓
Assertion	2thALT	⊢ ( 𝜑 ↔ 𝜓 )

Proof

Step	Hyp	Ref	Expression
1		2thALT.1	⊢ 𝜑
2		2thALT.2	⊢ 𝜓
3		pm5.1im	⊢ ( 𝜑 → ( 𝜓 → ( 𝜑 ↔ 𝜓 ) ) )
4	1 2 3	mp2	⊢ ( 𝜑 ↔ 𝜓 )