Theorem syl3an2b

Description: A syllogism inference. (Contributed by NM, 22-Aug-1995)

	Ref	Expression
Hypotheses	syl3an2b.1	$$⊢\phi \leftrightarrow \chi$$
	syl3an2b.2	$$⊢\left(\psi \wedge \chi \wedge \theta \right)\to \tau$$
Assertion	syl3an2b	$$⊢\left(\psi \wedge \phi \wedge \theta \right)\to \tau$$

Proof

Step	Hyp	Ref	Expression
1		syl3an2b.1	$$⊢\phi \leftrightarrow \chi$$
2		syl3an2b.2	$$⊢\left(\psi \wedge \chi \wedge \theta \right)\to \tau$$
3	1	biimpi	$$⊢\phi \to \chi$$
4	3 2	syl3an2	$$⊢\left(\psi \wedge \phi \wedge \theta \right)\to \tau$$