Theorem tsor2

Description: A Tseitin axiom for logical disjunction, in deduction form. (Contributed by Giovanni Mascellani, 25-Mar-2018)

	Ref	Expression
Assertion	tsor2	$$⊢\theta \to \left(\neg \phi \vee \left(\phi \vee \psi \right)\right)$$

Proof

Step	Hyp	Ref	Expression
1		orc	$$⊢\phi \to \left(\phi \vee \psi \right)$$
2	1	imori	$$⊢\left(\neg \phi \vee \left(\phi \vee \psi \right)\right)$$
3	2	a1i	$$⊢\theta \to \left(\neg \phi \vee \left(\phi \vee \psi \right)\right)$$