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Theorem ts3or1 33631
 Description: A Tseitin axiom for triple logical disjunction, in deduction form. (Contributed by Giovanni Mascellani, 25-Mar-2018.)
Assertion
Ref Expression
ts3or1 (𝜃 → (((𝜑𝜓) ∨ 𝜒) ∨ ¬ (𝜑𝜓𝜒)))

Proof of Theorem ts3or1
StepHypRef Expression
1 exmidd 432 . 2 (𝜃 → (((𝜑𝜓) ∨ 𝜒) ∨ ¬ ((𝜑𝜓) ∨ 𝜒)))
2 df-3or 1037 . . . 4 ((𝜑𝜓𝜒) ↔ ((𝜑𝜓) ∨ 𝜒))
32notbii 310 . . 3 (¬ (𝜑𝜓𝜒) ↔ ¬ ((𝜑𝜓) ∨ 𝜒))
43orbi2i 541 . 2 ((((𝜑𝜓) ∨ 𝜒) ∨ ¬ (𝜑𝜓𝜒)) ↔ (((𝜑𝜓) ∨ 𝜒) ∨ ¬ ((𝜑𝜓) ∨ 𝜒)))
51, 4sylibr 224 1 (𝜃 → (((𝜑𝜓) ∨ 𝜒) ∨ ¬ (𝜑𝜓𝜒)))
 Colors of variables: wff setvar class Syntax hints:  ¬ wn 3   → wi 4   ∨ wo 383   ∨ w3o 1035 This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8 This theorem depends on definitions:  df-bi 197  df-or 385  df-3or 1037 This theorem is referenced by: (None)
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