Theorem pm2.61d

Description: Deduction eliminating an antecedent. (Contributed by NM, 27-Apr-1994) (Proof shortened by Wolf Lammen, 12-Sep-2013)

	Ref	Expression
Hypotheses	pm2.61d.1	|- ( ph -> ( ps -> ch ) )
	pm2.61d.2	|- ( ph -> ( -. ps -> ch ) )
Assertion	pm2.61d	|- ( ph -> ch )

Proof

Step	Hyp	Ref	Expression
1		pm2.61d.1	|- ( ph -> ( ps -> ch ) )
2		pm2.61d.2	|- ( ph -> ( -. ps -> ch ) )
3	2	con1d	|- ( ph -> ( -. ch -> ps ) )
4	3 1	syld	|- ( ph -> ( -. ch -> ch ) )
5	4	pm2.18d	|- ( ph -> ch )