Theorem frege55aid

Description: Lemma for frege57aid . Core proof of Proposition 55 of Frege1879 p. 50. (Contributed by RP, 24-Dec-2019)

	Ref	Expression
Assertion	frege55aid	⊢ ( ( 𝜑 ↔ 𝜓 ) → ( 𝜓 ↔ 𝜑 ) )

Proof

Step	Hyp	Ref	Expression
1		bicom1	⊢ ( ( 𝜑 ↔ 𝜓 ) → ( 𝜓 ↔ 𝜑 ) )