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Mirrors > Home > NFE Home > Th. List > pm5.21ni | Unicode version |
Description: Two propositions implying a false one are equivalent. (Contributed by NM, 16-Feb-1996.) (Proof shortened by Wolf Lammen, 19-May-2013.) |
Ref | Expression |
---|---|
pm5.21ni.1 |
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pm5.21ni.2 |
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Ref | Expression |
---|---|
pm5.21ni |
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Step | Hyp | Ref | Expression |
---|---|---|---|
1 | pm5.21ni.1 |
. . 3
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2 | 1 | con3i 127 |
. 2
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3 | pm5.21ni.2 |
. . 3
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4 | 3 | con3i 127 |
. 2
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5 | 2, 4 | 2falsed 340 |
1
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Colors of variables: wff setvar class |
Syntax hints: ![]() ![]() ![]() |
This theorem was proved from axioms: ax-mp 5 ax-1 6 ax-2 7 ax-3 8 |
This theorem depends on definitions: df-bi 177 |
This theorem is referenced by: pm5.21nii 342 pm5.54 870 niabn 917 ndmovord 5621 |
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