nnexmid - Intuitionistic Logic Explorer

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Theorem nnexmid 855

Description: Double negation of decidability of a formula. See also comment of nndc 856 to avoid a pitfall that could come from the label "nnexmid". This theorem can also be proved from bj-nnor 16056 as in bj-nndcALT 16080. (Contributed by BJ, 9-Oct-2019.)

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

**Proof of Theorem nnexmid**
Step	Hyp	Ref	Expression
1		pm3.24 698	. 2 $/\$
2		ioran 757	. 2 $\/$ $/\$
3	1, 2	mtbir 675	1 $\/$

Colors of variables: wff set class

Syntax hints:

wn 3 $/\$ wa 104 $\/$ wo 713

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 617 ax-in2 618 ax-io 714

This theorem depends on definitions: df-bi 117

This theorem is referenced by: nndc 856 dcfromnotnotr 1490 dcfromcon 1491 exmid1stab 4291

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