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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

Colors of variables: wff setvar class

Syntax hints:

wn 3

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

This theorem is referenced by: nbn3 348 fal 1381 ax6dgen 1768 mdegleb 22192 nextnt 29297 amosym1 29318 aisbnaxb 31392