nnexmid - Intuitionistic Logic Explorer

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Theorem nnexmid 862

Description: Double negation of decidability of a formula. See also comment of nndc 863 to avoid a pitfall that could come from the label "nnexmid". This theorem can also be proved from bj-nnor 16676 as in bj-nndcALT 16700. (Contributed by BJ, 9-Oct-2019.)

**Assertion**
Ref	Expression
nnexmid	$\/$

**Proof of Theorem nnexmid**
Step	Hyp	Ref	Expression
1		pm3.24 705	. 2 $/\$
2		ioran 764	. 2 $\/$ $/\$
3	1, 2	mtbir 682	1 $\/$

Colors of variables: wff set class

Syntax hints:

wn 3 $/\$ wa 104 $\/$ wo 720

This theorem was proved from axioms: ax-mp 5 ax-1 6 ax-2 7 ax-ia1 106 ax-ia2 107 ax-ia3 108 ax-in1 623 ax-in2 624 ax-io 721

This theorem depends on definitions: df-bi 117

This theorem is referenced by: nndc 863 dcfromnotnotr 1497 dcfromcon 1498 exmid1stab 4340

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