Theorem notnoti

Description: Inference associated with notnot . (Contributed by NM, 27-Feb-2008)

	Ref	Expression
Hypothesis	notnoti.1	|- ph
Assertion	notnoti	|- -. -. ph

Proof

Step	Hyp	Ref	Expression
1		notnoti.1	|- ph
2		notnot	|- ( ph -> -. -. ph )
3	1 2	ax-mp	|- -. -. ph