Theorem wl-luk-a1i

Description: Inference rule. Copy of a1i with a different proof. (Contributed by Wolf Lammen, 17-Dec-2018) (New usage is discouraged.) (Proof modification is discouraged.)

	Ref	Expression
Hypothesis	wl-luk-a1i.1	$$⊢\phi$$
Assertion	wl-luk-a1i	$$⊢\psi \to \phi$$

Proof

Step	Hyp	Ref	Expression
1		wl-luk-a1i.1	$$⊢\phi$$
2	1	wl-luk-pm2.24i	$$⊢\neg \phi \to \neg \psi$$
3	2	wl-luk-con4i	$$⊢\psi \to \phi$$