Theorem imbitrid

Description: A mixed syllogism inference. (Contributed by NM, 12-Jan-1993)

	Ref	Expression
Hypotheses	imbitrid.1	|- ( ph -> ps )
	imbitrid.2	|- ( ch -> ( ps <-> th ) )
Assertion	imbitrid	|- ( ch -> ( ph -> th ) )

Proof

Step	Hyp	Ref	Expression
1		imbitrid.1	|- ( ph -> ps )
2		imbitrid.2	|- ( ch -> ( ps <-> th ) )
3	2	biimpd	|- ( ch -> ( ps -> th ) )
4	1 3	syl5	|- ( ch -> ( ph -> th ) )