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Theorem axfrege41 36957
Description: Identical to notnot 134. Axiom 41 of [Frege1879] p. 47. (Contributed by RP, 24-Dec-2019.)
Assertion
Ref Expression
axfrege41 (𝜑 → ¬ ¬ 𝜑)

Proof of Theorem axfrege41
StepHypRef Expression
1 notnot 134 1 (𝜑 → ¬ ¬ 𝜑)
Colors of variables: wff setvar class
Syntax hints:  ¬ wn 3  wi 4
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8
This theorem is referenced by: (None)
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