notnotnot - Intuitionistic Logic Explorer

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Theorem notnotnot 624

Description: Triple negation is equivalent to negation. (Contributed by Jim Kingdon, 28-Jul-2018.)

**Assertion**
Ref	Expression
notnotnot

**Proof of Theorem notnotnot**
Step	Hyp	Ref	Expression
1		notnot 619	. . 3
2	1	con3i 622	. 2
3		notnot 619	. 2
4	2, 3	impbii 125	1

Colors of variables: wff set class

Syntax hints:

wn 3

wb 104

This theorem was proved from axioms: ax-mp 5 ax-1 6 ax-2 7 ax-ia2 106 ax-ia3 107 ax-in1 604 ax-in2 605

This theorem depends on definitions: df-bi 116

This theorem is referenced by: stabnot 823 dcnnOLD 839 bj-nnsn 13614