Theorem axfrege54a

Description: Justification for ax-frege54a . Identical to biid . (Contributed by RP, 24-Dec-2019)

	Ref	Expression
Assertion	axfrege54a	$$⊢\phi \leftrightarrow \phi$$

Proof

Step	Hyp	Ref	Expression
1		biid	$$⊢\phi \leftrightarrow \phi$$