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Theorem notnotd 570
Description: Deduction associated with notnot 569 and notnoti 584. (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 569 . 2 (𝜓 → ¬ ¬ 𝜓)
31, 2syl 14 1 (𝜑 → ¬ ¬ 𝜓)
Colors of variables: wff set class
Syntax hints:  ¬ wn 3  wi 4
This theorem was proved from axioms:  ax-1 5  ax-2 6  ax-mp 7  ax-in1 554  ax-in2 555
This theorem is referenced by:  mod2eq1n2dvds  10183
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