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Mirrors > Home > NFE Home > Th. List > biorf | Unicode version |
Description: A wff is equivalent to its disjunction with falsehood. Theorem *4.74 of [WhiteheadRussell] p. 121. (Contributed by NM, 23-Mar-1995.) (Proof shortened by Wolf Lammen, 18-Nov-2012.) |
Ref | Expression |
---|---|
biorf |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | olc 373 | . 2 | |
2 | orel1 371 | . 2 | |
3 | 1, 2 | impbid2 195 | 1 |
Colors of variables: wff setvar class |
Syntax hints: wn 3 wi 4 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: biortn 395 pm5.61 693 pm5.55 867 cadan 1392 euor 2231 eueq3 3011 unineq 3505 ifor 3702 difprsnss 3846 eqtfinrelk 4486 dfphi2 4569 |
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