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Theorem pm2.521dcALT 870
Description: Alternate proof of pm2.521dc 869. (Contributed by Jim Kingdon, 5-May-2018.) (Proof modification is discouraged.) (New usage is discouraged.)
Assertion
Ref Expression
pm2.521dcALT (DECID 𝜑 → (¬ (𝜑𝜓) → (𝜓𝜑)))

Proof of Theorem pm2.521dcALT
StepHypRef Expression
1 pm2.52 656 . 2 (¬ (𝜑𝜓) → (¬ 𝜑 → ¬ 𝜓))
2 condc 853 . 2 (DECID 𝜑 → ((¬ 𝜑 → ¬ 𝜓) → (𝜓𝜑)))
31, 2syl5 32 1 (DECID 𝜑 → (¬ (𝜑𝜓) → (𝜓𝜑)))
Colors of variables: wff set class
Syntax hints:  ¬ wn 3  wi 4  DECID wdc 834
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-ia1 106  ax-ia2 107  ax-ia3 108  ax-in1 614  ax-in2 615  ax-io 709
This theorem depends on definitions:  df-bi 117  df-stab 831  df-dc 835
This theorem is referenced by: (None)
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