Theorem syl121anc

Description: Syllogism combined with contraction. (Contributed by NM, 11-Mar-2012)

	Ref	Expression
Hypotheses	syl3anc.1	|- ( ph -> ps )
	syl3anc.2	|- ( ph -> ch )
	syl3anc.3	|- ( ph -> th )
	syl3Xanc.4	|- ( ph -> ta )
	syl121anc.5	|- ( ( ps /\ ( ch /\ th ) /\ ta ) -> et )
Assertion	syl121anc	|- ( ph -> et )

Proof

Step	Hyp	Ref	Expression
1		syl3anc.1	|- ( ph -> ps )
2		syl3anc.2	|- ( ph -> ch )
3		syl3anc.3	|- ( ph -> th )
4		syl3Xanc.4	|- ( ph -> ta )
5		syl121anc.5	|- ( ( ps /\ ( ch /\ th ) /\ ta ) -> et )
6	2 3	jca	|- ( ph -> ( ch /\ th ) )
7	1 6 4 5	syl3anc	|- ( ph -> et )