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Theorem notnoti 552
Description: Infer double negation. (Contributed by NM, 27-Feb-2008.)
Hypothesis
Ref Expression
negbi.1 φ
Assertion
Ref Expression
notnoti ¬ ¬ φ

Proof of Theorem notnoti
StepHypRef Expression
1 negbi.1 . 2 φ
2 notnot1 540 . 2 (φ → ¬ ¬ φ)
31, 2ax-mp 7 1 ¬ ¬ φ
Colors of variables: wff set class
Syntax hints:  ¬ wn 3
This theorem is referenced by:  nbn3  594  fal  1204  ax-9  1354
This theorem was proved from axioms:  ax-1 5  ax-2 6  ax-mp 7  ax-in1 526  ax-in2 527
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