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Theorem axfrege41 38138
Description: Identical to notnot 136. Axiom 41 of [Frege1879] p. 47. (Contributed by RP, 24-Dec-2019.)
Assertion
Ref Expression
axfrege41  |-  ( ph  ->  -.  -.  ph )

Proof of Theorem axfrege41
StepHypRef Expression
1 notnot 136 1  |-  ( ph  ->  -.  -.  ph )
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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