Theorem pm2.61d2

Description: Inference eliminating an antecedent. (Contributed by NM, 18-Aug-1993)

	Ref	Expression
Hypotheses	pm2.61d2.1	$$⊢\phi \to \left(\neg \psi \to \chi \right)$$
	pm2.61d2.2	$$⊢\psi \to \chi$$
Assertion	pm2.61d2	$$⊢\phi \to \chi$$

Proof

Step	Hyp	Ref	Expression
1		pm2.61d2.1	$$⊢\phi \to \left(\neg \psi \to \chi \right)$$
2		pm2.61d2.2	$$⊢\psi \to \chi$$
3	2	a1i	$$⊢\phi \to \left(\psi \to \chi \right)$$
4	3 1	pm2.61d	$$⊢\phi \to \chi$$