Theorem wl-a1i 33251

Description: Inference rule. Copy of a1i 11 with a different proof. (Contributed by Wolf Lammen, 17-Dec-2018.) (New usage is discouraged.) (Proof modification is discouraged.)

Hypothesis

Ref	Expression
wl-a1i.1	⊢ 𝜑

Assertion

Ref	Expression
wl-a1i	⊢ (𝜓 → 𝜑)

Proof of Theorem wl-a1i

Step	Hyp	Ref	Expression
1		wl-a1i.1	. . 3 ⊢ 𝜑
2	1	wl-pm2.24i 33250	. 2 ⊢ (¬ 𝜑 → ¬ 𝜓)
3	2	wl-con4i 33249	1 ⊢ (𝜓 → 𝜑)

Syntax hints:  ¬ wn 3   → wi 4

This theorem was proved from axioms:  ax-mp 5  ax-luk1 33241  ax-luk2 33242  ax-luk3 33243

This theorem is referenced by:  wl-mpi  33252  wl-impchain-a1-1  33283