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Theorem notnotri 106
Description: Inference from double negation. (Contributed by NM, 27-Feb-2008.)
Hypothesis
Ref Expression
notnotri.1 ¬ ¬ φ
Assertion
Ref Expression
notnotri φ

Proof of Theorem notnotri
StepHypRef Expression
1 notnotri.1 . 2 ¬ ¬ φ
2 notnot2 104 . 2 (¬ ¬ φφ)
31, 2ax-mp 5 1 φ
Colors of variables: wff setvar class
Syntax hints:  ¬ wn 3
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8
This theorem is referenced by:  mt3  171  mtp-xor  1536
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