pm2.1 - New Foundations Explorer

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Theorem pm2.1 406

Description: Theorem *2.1 of [WhiteheadRussell] p. 101. (Contributed by NM, 3-Jan-2005.) (Proof shortened by Wolf Lammen, 23-Nov-2012.)

**Assertion**
Ref	Expression
pm2.1	$\/$

**Proof of Theorem pm2.1**
Step	Hyp	Ref	Expression
1		id 19	. 2
2	1	imori 402	1 $\/$

Colors of variables: wff setvar class

This proof depends on syntax axioms:

wn 3 $\/$ wo 357

This proof depends on axioms: ax-mp 5 ax-1 6 ax-2 7 ax-3 8

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

This theorem is used by: nchoicelem9 6298 nchoicelem18 6307