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Theorem contrd 35686
 Description: A proof by contradiction, in deduction form. (Contributed by Giovanni Mascellani, 19-Mar-2018.)
Hypotheses
Ref Expression
contrd.1 (𝜑 → (¬ 𝜓𝜒))
contrd.2 (𝜑 → (¬ 𝜓 → ¬ 𝜒))
Assertion
Ref Expression
contrd (𝜑𝜓)

Proof of Theorem contrd
StepHypRef Expression
1 contrd.1 . . 3 (𝜑 → (¬ 𝜓𝜒))
2 contrd.2 . . 3 (𝜑 → (¬ 𝜓 → ¬ 𝜒))
31, 2jcad 516 . 2 (𝜑 → (¬ 𝜓 → (𝜒 ∧ ¬ 𝜒)))
4 pm2.24 124 . . . . 5 (𝜒 → (¬ 𝜒𝜓))
54imp 410 . . . 4 ((𝜒 ∧ ¬ 𝜒) → 𝜓)
65imim2i 16 . . 3 ((¬ 𝜓 → (𝜒 ∧ ¬ 𝜒)) → (¬ 𝜓𝜓))
76pm2.18d 127 . 2 ((¬ 𝜓 → (𝜒 ∧ ¬ 𝜒)) → 𝜓)
83, 7syl 17 1 (𝜑𝜓)
 Colors of variables: wff setvar class Syntax hints:  ¬ wn 3   → wi 4   ∧ wa 399 This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8 This theorem depends on definitions:  df-bi 210  df-an 400 This theorem is referenced by:  mpobi123f  35751  mptbi12f  35755  ac6s6  35761
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