Theorem bj-biorfi

Description: This should be labeled "biorfi" while the current biorfi should be labeled "biorfri". The dual of biorf is not biantr but iba (and ibar ). So there should also be a "biorfr". (Note that these four statements can actually be strengthened to biconditionals.) (Contributed by BJ, 26-Oct-2019) (Proof modification is discouraged.)

	Ref	Expression
Hypothesis	bj-biorfi.1	$$⊢\neg \phi$$
Assertion	bj-biorfi	$$⊢\psi \leftrightarrow \left(\phi \vee \psi \right)$$

Proof

Step	Hyp	Ref	Expression
1		bj-biorfi.1	$$⊢\neg \phi$$
2		biorf	$$⊢\neg \phi \to \left(\psi \leftrightarrow \left(\phi \vee \psi \right)\right)$$
3	1 2	ax-mp	$$⊢\psi \leftrightarrow \left(\phi \vee \psi \right)$$