Theorem pm2.01da

Description: Deduction based on reductio ad absurdum. See pm2.01 . (Contributed by Mario Carneiro, 9-Feb-2017)

	Ref	Expression
Hypothesis	pm2.01da.1	|- ( ( ph /\ ps ) -> -. ps )
Assertion	pm2.01da	|- ( ph -> -. ps )

Proof

Step	Hyp	Ref	Expression
1		pm2.01da.1	|- ( ( ph /\ ps ) -> -. ps )
2	1	ex	|- ( ph -> ( ps -> -. ps ) )
3	2	pm2.01d	|- ( ph -> -. ps )