Theorem notnoti 123

Description: Infer double negation. (Contributed by NM, 27-Feb-2008.)

Hypothesis

Ref	Expression
negbi.1

Assertion

Ref	Expression
notnoti

Proof of Theorem notnoti

Step	Hyp	Ref	Expression
1		negbi.1	. 2
2		notnot1 122	. 2
3	1, 2	ax-mp 5	1

Syntax hints:  -.wn 3

This theorem is referenced by:  nbn3  348  fal  1402  ax6dgen  1824  mdegleb  22464  nextnt  29870  amosym1  29891  aisbnaxb  32106

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8