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Theorem orel1 371

Description: Elimination of disjunction by denial of a disjunct. Theorem *2.55 of [WhiteheadRussell] p. 107. (Contributed by NM, 12-Aug-1994.) (Proof shortened by Wolf Lammen, 21-Jul-2012.)

**Assertion**
Ref	Expression
orel1	$\/$

**Proof of Theorem orel1**
Step	Hyp	Ref	Expression
1		pm2.53 362	. 2 $\/$
2	1	com12 27	1 $\/$

Colors of variables: wff setvar class

Syntax hints:

wn 3

wi 4 $\/$ wo 357

This theorem was proved from axioms: ax-1 5 ax-2 6 ax-3 7 ax-mp 8

This theorem depends on definitions: df-bi 177 df-or 359

This theorem is referenced by: pm2.25 393 biorf 394 euor2 2272 nndisjeq 4429 nnceleq 4430 sfinltfin 4535 sfin111 4536 phialllem1 4616 xpcan 5057 funun 5146 enprmaplem3 6078

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