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Theorem imordc 796
 Description: Implication in terms of disjunction for a decidable proposition. Based on theorem *4.6 of [WhiteheadRussell] p. 120. The reverse direction, imorr 797, holds for all propositions. (Contributed by Jim Kingdon, 20-Apr-2018.)
Assertion
Ref Expression
imordc (DECID 𝜑 → ((𝜑𝜓) ↔ (¬ 𝜑𝜓)))

Proof of Theorem imordc
StepHypRef Expression
1 notnotbdc 766 . . 3 (DECID 𝜑 → (𝜑 ↔ ¬ ¬ 𝜑))
21imbi1d 220 . 2 (DECID 𝜑 → ((𝜑𝜓) ↔ (¬ ¬ 𝜑𝜓)))
3 dcn 746 . . 3 (DECID 𝜑DECID ¬ 𝜑)
4 dfordc 791 . . 3 (DECID ¬ 𝜑 → ((¬ 𝜑𝜓) ↔ (¬ ¬ 𝜑𝜓)))
53, 4syl 14 . 2 (DECID 𝜑 → ((¬ 𝜑𝜓) ↔ (¬ ¬ 𝜑𝜓)))
62, 5bitr4d 180 1 (DECID 𝜑 → ((𝜑𝜓) ↔ (¬ 𝜑𝜓)))
 Colors of variables: wff set class Syntax hints:  ¬ wn 3   → wi 4   ↔ wb 98   ∨ wo 629  DECID wdc 742 This theorem was proved from axioms:  ax-1 5  ax-2 6  ax-mp 7  ax-ia1 99  ax-ia2 100  ax-ia3 101  ax-in1 544  ax-in2 545  ax-io 630 This theorem depends on definitions:  df-bi 110  df-dc 743 This theorem is referenced by:  pm4.62dc  798  pm2.26dc  813  nf4dc  1560  algcvgblem  9888
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