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Mirrors > Home > ILE Home > Th. List > orel2 | Unicode version |
Description: Elimination of disjunction by denial of a disjunct. Theorem *2.56 of [WhiteheadRussell] p. 107. (Contributed by NM, 12-Aug-1994.) (Proof shortened by Wolf Lammen, 5-Apr-2013.) |
Ref | Expression |
---|---|
orel2 |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | idd 21 | . 2 | |
2 | pm2.21 591 | . 2 | |
3 | 1, 2 | jaod 691 | 1 |
Colors of variables: wff set class |
Syntax hints: wn 3 wi 4 wo 682 |
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-in2 589 ax-io 683 |
This theorem depends on definitions: df-bi 116 |
This theorem is referenced by: biorfi 720 pm2.64 775 stdcn 817 pm5.71dc 930 ecased 1312 19.30dc 1591 dveeq2 1771 prel12 3668 funun 5137 |
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