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Theorem pm2.21ddALT 117
Description: Alternate proof of pm2.21dd 184. (Contributed by Mario Carneiro, 9-Feb-2017.) (Proof modification is discouraged.) (New usage is discouraged.)
Hypotheses
Ref Expression
pm2.21ddALT.1 (𝜑𝜓)
pm2.21ddALT.2 (𝜑 → ¬ 𝜓)
Assertion
Ref Expression
pm2.21ddALT (𝜑𝜒)

Proof of Theorem pm2.21ddALT
StepHypRef Expression
1 pm2.21ddALT.1 . 2 (𝜑𝜓)
2 pm2.21ddALT.2 . . 3 (𝜑 → ¬ 𝜓)
32pm2.21d 116 . 2 (𝜑 → (𝜓𝜒))
41, 3mpd 15 1 (𝜑𝜒)
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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