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Mirrors > Home > ILE Home > Th. List > notnotnot | Unicode version |
Description: Triple negation is equivalent to negation. (Contributed by Jim Kingdon, 28-Jul-2018.) |
Ref | Expression |
---|---|
notnotnot |
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Step | Hyp | Ref | Expression |
---|---|---|---|
1 | notnot 619 |
. . 3
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2 | 1 | con3i 622 |
. 2
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3 | notnot 619 |
. 2
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4 | 2, 3 | impbii 125 |
1
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Colors of variables: wff set class |
Syntax hints: ![]() ![]() |
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 819 dcnnOLD 835 bj-nnsn 13116 |
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