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Mirrors > Home > ILE Home > Th. List > nbn2 | Unicode version |
Description: The negation of a wff is equivalent to the wff's equivalence to falsehood. (Contributed by Juha Arpiainen, 19-Jan-2006.) (Revised by Mario Carneiro, 31-Jan-2015.) |
Ref | Expression |
---|---|
nbn2 |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | pm5.21im 644 | . 2 | |
2 | bi2 128 | . . 3 | |
3 | mtt 642 | . . 3 | |
4 | 2, 3 | syl5ibr 154 | . 2 |
5 | 1, 4 | impbid 127 | 1 |
Colors of variables: wff set class |
Syntax hints: wn 3 wi 4 wb 103 |
This theorem was proved from axioms: ax-1 5 ax-2 6 ax-mp 7 ax-ia1 104 ax-ia2 105 ax-ia3 106 ax-in1 576 ax-in2 577 |
This theorem depends on definitions: df-bi 115 |
This theorem is referenced by: bibif 646 pm5.18dc 810 biassdc 1326 |
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