Theorem jarl

Description: Elimination of a nested antecedent. (Contributed by Wolf Lammen, 10-May-2013)

	Ref	Expression
Assertion	jarl	$$⊢\left(\left(\phi \to \psi \right)\to \chi \right)\to \left(\neg \phi \to \chi \right)$$

Proof

Step	Hyp	Ref	Expression
1		pm2.21	$$⊢\neg \phi \to \left(\phi \to \psi \right)$$
2	1	imim1i	$$⊢\left(\left(\phi \to \psi \right)\to \chi \right)\to \left(\neg \phi \to \chi \right)$$