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Theorem nic-idbl 1451

Description: Double the terms. Since doubling is the same as negation, this can be viewed as a contraposition inference. (Contributed by Jeff Hoffman, 17-Nov-2007.) (Proof modification is discouraged.) (New usage is discouraged.)

**Hypothesis**
Ref	Expression
nic-idbl.1	$-/\$ $-/\$

**Assertion**
Ref	Expression
nic-idbl	$-/\$ $-/\$ $-/\$ $-/\$ $-/\$

**Proof of Theorem nic-idbl**
Step	Hyp	Ref	Expression
1		nic-idbl.1	. . 3 $-/\$ $-/\$
2	1	nic-imp 1440	. 2 $-/\$ $-/\$ $-/\$ $-/\$ $-/\$
3	1	nic-imp 1440	. 2 $-/\$ $-/\$ $-/\$ $-/\$ $-/\$
4	2, 3	nic-ich 1450	1 $-/\$ $-/\$ $-/\$ $-/\$ $-/\$

Colors of variables: wff setvar class

Syntax hints: $-/\$ wnan 1287

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-an 360 df-nan 1288

This theorem is referenced by: nic-luk1 1456

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