Theorem sylbird

Description: A syllogism deduction. (Contributed by NM, 3-Aug-1994)

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

Proof

Step	Hyp	Ref	Expression
1		sylbird.1	|- ( ph -> ( ch <-> ps ) )
2		sylbird.2	|- ( ph -> ( ch -> th ) )
3	1	biimprd	|- ( ph -> ( ps -> ch ) )
4	3 2	syld	|- ( ph -> ( ps -> th ) )