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Theorem notnotd 138
Description: Deduction associated with notnot 136 and notnoti 137. (Contributed by Jarvin Udandy, 2-Sep-2016.) Avoid biconditional. (Revised by Wolf Lammen, 27-Mar-2021.)
Hypothesis
Ref Expression
notnotd.1 (𝜑𝜓)
Assertion
Ref Expression
notnotd (𝜑 → ¬ ¬ 𝜓)

Proof of Theorem notnotd
StepHypRef Expression
1 notnotd.1 . 2 (𝜑𝜓)
2 notnot 136 . 2 (𝜓 → ¬ ¬ 𝜓)
31, 2syl 17 1 (𝜑 → ¬ ¬ 𝜓)
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:  eupth2lemb  27310  xrdifh  29772  amosym1  32652  nnfoctbdjlem  41092  lighneallem1  41949  lighneallem3  41951  lindslinindsimp2  42679
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