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Mirrors > Home > NFE Home > Th. List > oridm | Unicode version |
Description: Idempotent law for disjunction. Theorem *4.25 of [WhiteheadRussell] p. 117. (Contributed by NM, 5-Aug-1993.) (Proof shortened by Andrew Salmon, 16-Apr-2011.) (Proof shortened by Wolf Lammen, 10-Mar-2013.) |
Ref | Expression |
---|---|
oridm |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | pm1.2 499 | . 2 | |
2 | pm2.07 385 | . 2 | |
3 | 1, 2 | impbii 180 | 1 |
Colors of variables: wff setvar class |
Syntax hints: wb 176 wo 357 |
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 df-or 359 |
This theorem is referenced by: pm4.25 501 orordi 516 orordir 517 truortru 1340 falorfal 1343 unidm 3408 |
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