Theorem pm2.1dc 822

Description: Commuted law of the excluded middle for a decidable proposition. Based on theorem *2.1 of [WhiteheadRussell] p. 101. (Contributed by Jim Kingdon, 25-Mar-2018.)

Assertion

Ref	Expression
pm2.1dc	⊢ (DECID 𝜑 → (¬ 𝜑 ∨ 𝜑))

Proof of Theorem pm2.1dc

Step	Hyp	Ref	Expression
1		df-dc 820	. . 3 ⊢ (DECID 𝜑 ↔ (𝜑 ∨ ¬ 𝜑))
2		orcom 717	. . 3 ⊢ ((𝜑 ∨ ¬ 𝜑) ↔ (¬ 𝜑 ∨ 𝜑))
3	1, 2	bitri 183	. 2 ⊢ (DECID 𝜑 ↔ (¬ 𝜑 ∨ 𝜑))
4	3	biimpi 119	1 ⊢ (DECID 𝜑 → (¬ 𝜑 ∨ 𝜑))

Syntax hints:  ¬ wn 3   → wi 4   ∨ wo 697  DECID wdc 819

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-ia1 105  ax-ia2 106  ax-ia3 107  ax-io 698

This theorem depends on definitions:  df-bi 116  df-dc 820

This theorem is referenced by:  pm2.6dc  847  rabrsndc  3586