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Theorem negai 85
Description: Inference from double negation.
Hypothesis
Ref Expression
negai.1 |- -. -. ph
Assertion
Ref Expression
negai |- ph

Proof of Theorem negai
StepHypRef Expression
1 negai.1 . 2 |- -. -. ph
2 nega 84 . 2 |- (-. -. ph -> ph)
31, 2ax-mp 7 1 |- ph
Colors of variables: wff set class
Syntax hints:  -. wn 2
This theorem was proved from axioms:  ax-1 4  ax-2 5  ax-3 6  ax-mp 7
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