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Theorem tsbi4 34429
Description: A Tseitin axiom for logical biimplication, in deduction form. (Contributed by Giovanni Mascellani, 24-Mar-2018.)
Assertion
Ref Expression
tsbi4 (𝜃 → ((¬ 𝜑𝜓) ∨ ¬ (𝜑𝜓)))

Proof of Theorem tsbi4
StepHypRef Expression
1 tsbi3 34428 . 2 (𝜃 → ((𝜓 ∨ ¬ 𝜑) ∨ ¬ (𝜓𝜑)))
2 orcom 897 . . 3 ((𝜓 ∨ ¬ 𝜑) ↔ (¬ 𝜑𝜓))
3 bicom 214 . . . 4 ((𝜓𝜑) ↔ (𝜑𝜓))
43notbii 312 . . 3 (¬ (𝜓𝜑) ↔ ¬ (𝜑𝜓))
52, 4orbi12i 939 . 2 (((𝜓 ∨ ¬ 𝜑) ∨ ¬ (𝜓𝜑)) ↔ ((¬ 𝜑𝜓) ∨ ¬ (𝜑𝜓)))
61, 5sylib 210 1 (𝜃 → ((¬ 𝜑𝜓) ∨ ¬ (𝜑𝜓)))
Colors of variables: wff setvar class
Syntax hints:  ¬ wn 3  wi 4  wb 198  wo 874
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 199  df-or 875
This theorem is referenced by:  tsxo4  34433  mpt2bi123f  34457  mptbi12f  34461  ac6s6  34466
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