Theorem wl-luk-con4i

Description: Inference rule. Copy of con4i with a different proof. (Contributed by Wolf Lammen, 17-Dec-2018) (New usage is discouraged.) (Proof modification is discouraged.)

	Ref	Expression
Hypothesis	wl-luk-con4i.1	$$⊢\neg \phi \to \neg \psi$$
Assertion	wl-luk-con4i	$$⊢\psi \to \phi$$

Proof

Step	Hyp	Ref	Expression
1		wl-luk-con4i.1	$$⊢\neg \phi \to \neg \psi$$
2		ax-luk3	$$⊢\psi \to \left(\neg \psi \to \phi \right)$$
3	1 2	wl-luk-imtrid	$$⊢\psi \to \left(\neg \phi \to \phi \right)$$
4	3	wl-luk-pm2.18d	$$⊢\psi \to \phi$$