Theorem syl3an1b

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

	Ref	Expression
Hypotheses	syl3an1b.1	|- ( ph <-> ps )
	syl3an1b.2	|- ( ( ps /\ ch /\ th ) -> ta )
Assertion	syl3an1b	|- ( ( ph /\ ch /\ th ) -> ta )

Proof

Step	Hyp	Ref	Expression
1		syl3an1b.1	|- ( ph <-> ps )
2		syl3an1b.2	|- ( ( ps /\ ch /\ th ) -> ta )
3	1	biimpi	|- ( ph -> ps )
4	3 2	syl3an1	|- ( ( ph /\ ch /\ th ) -> ta )