Theorem bj-mt2bi

Description: Version of mt2 where the major premise is a biconditional. Shortens fal (see bj-fal ) . Another proof is also possible via con2bii and mpbi . The current mt2bi should be relabeled, maybe to imfal. (Contributed by BJ, 5-Oct-2024)

	Ref	Expression
Hypotheses	bj-mt2bi.maj	$$⊢\psi \leftrightarrow \neg \phi$$
	bj-mt2bi.min	$$⊢\phi$$
Assertion	bj-mt2bi	$$⊢\neg \psi$$

Proof

Step	Hyp	Ref	Expression
1		bj-mt2bi.maj	$$⊢\psi \leftrightarrow \neg \phi$$
2		bj-mt2bi.min	$$⊢\phi$$
3	1	biimpi	$$⊢\psi \to \neg \phi$$
4	2 3	mt2	$$⊢\neg \psi$$