notnotnot - Intuitionistic Logic Explorer

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Theorem notnotnot 628

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

**Assertion**
Ref	Expression
notnotnot

**Proof of Theorem notnotnot**
Step	Hyp	Ref	Expression
1		notnot 559	. . 3
2	1	con3i 562	. 2
3		notnot 559	. 2
4	2, 3	impbii 117	1

Colors of variables: wff set class

Syntax hints:

wn 3

wb 98

This theorem was proved from axioms: ax-1 5 ax-2 6 ax-mp 7 ax-ia2 100 ax-ia3 101 ax-in1 544 ax-in2 545

This theorem depends on definitions: df-bi 110

This theorem is referenced by: stabnot 741 testbitestn 823