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Theorem mth8 622
Description: Theorem 8 of [Margaris] p. 60. (Contributed by NM, 5-Aug-1993.) (Proof shortened by Josh Purinton, 29-Dec-2000.)
Assertion
Ref Expression
mth8 (𝜑 → (¬ 𝜓 → ¬ (𝜑𝜓)))

Proof of Theorem mth8
StepHypRef Expression
1 pm2.27 40 . 2 (𝜑 → ((𝜑𝜓) → 𝜓))
21con3d 603 1 (𝜑 → (¬ 𝜓 → ¬ (𝜑𝜓)))
Colors of variables: wff set class
Syntax hints:  ¬ wn 3  wi 4
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-in1 586  ax-in2 587
This theorem is referenced by:  bj-nnim  12749
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