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Mirrors > Home > ILE Home > Th. List > Mathboxes > bj-nnsn | Unicode version |
Description: As far as implying a negated formula is concerned, a formula is equivalent to its double negation. (Contributed by BJ, 24-Nov-2023.) |
Ref | Expression |
---|---|
bj-nnsn |
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Step | Hyp | Ref | Expression |
---|---|---|---|
1 | con3 632 |
. . . 4
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2 | 1 | con3d 621 |
. . 3
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3 | notnotnot 624 |
. . 3
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4 | 2, 3 | syl6ib 160 |
. 2
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5 | notnot 619 |
. . 3
![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() | |
6 | 5 | imim1i 60 |
. 2
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7 | 4, 6 | 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-ia1 105 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: (None) |
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