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Theorem pm2.521dc 869
Description: Theorem *2.521 of [WhiteheadRussell] p. 107, but with an additional decidability condition. Note that by replacing in proof pm2.52 656 with conax1k 654, we obtain a proof of the more general instance where the last occurrence of 𝜑 is replaced with any 𝜒. (Contributed by Jim Kingdon, 5-May-2018.)
Assertion
Ref Expression
pm2.521dc (DECID 𝜑 → (¬ (𝜑𝜓) → (𝜓𝜑)))

Proof of Theorem pm2.521dc
StepHypRef Expression
1 pm2.521gdc 868 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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