Theorem ja

Description: Inference joining the antecedents of two premises. For partial converses, see jarri and jarli . (Contributed by NM, 24-Jan-1993) (Proof shortened by Mel L. O'Cat, 19-Feb-2008)

	Ref	Expression
Hypotheses	ja.1	|- ( -. ph -> ch )
	ja.2	|- ( ps -> ch )
Assertion	ja	|- ( ( ph -> ps ) -> ch )

Proof

Step	Hyp	Ref	Expression
1		ja.1	|- ( -. ph -> ch )
2		ja.2	|- ( ps -> ch )
3	2	imim2i	|- ( ( ph -> ps ) -> ( ph -> ch ) )
4	3 1	pm2.61d1	|- ( ( ph -> ps ) -> ch )