Theorem norasslem2

Description: This lemma specializes biimt suitably for the proof of norass . (Contributed by Wolf Lammen, 18-Dec-2023)

	Ref	Expression
Assertion	norasslem2	$$⊢\phi \to \left(\psi \leftrightarrow \left(\left(\phi \vee \chi \right)\to \psi \right)\right)$$

Proof

Step	Hyp	Ref	Expression
1		orc	$$⊢\phi \to \left(\phi \vee \chi \right)$$
2		biimt	$$⊢\left(\phi \vee \chi \right)\to \left(\psi \leftrightarrow \left(\left(\phi \vee \chi \right)\to \psi \right)\right)$$
3	1 2	syl	$$⊢\phi \to \left(\psi \leftrightarrow \left(\left(\phi \vee \chi \right)\to \psi \right)\right)$$