Theorem wl-luk-con1i

Description: A contraposition inference. Copy of con1i with a different proof. (Contributed by Wolf Lammen, 17-Dec-2018) (New usage is discouraged.) (Proof modification is discouraged.)

	Ref	Expression
Hypothesis	wl-luk-con1i.1	$$⊢\neg \phi \to \psi$$
Assertion	wl-luk-con1i	$$⊢\neg \psi \to \phi$$

Proof

Step	Hyp	Ref	Expression
1		wl-luk-con1i.1	$$⊢\neg \phi \to \psi$$
2		wl-luk-pm2.21	$$⊢\neg \psi \to \left(\psi \to \phi \right)$$
3	1 2	wl-luk-imtrid	$$⊢\neg \psi \to \left(\neg \phi \to \phi \right)$$
4	3	wl-luk-pm2.18d	$$⊢\neg \psi \to \phi$$