Theorem pm2.24d

Description: Deduction form of pm2.24 . (Contributed by NM, 30-Jan-2006)

	Ref	Expression
Hypothesis	pm2.24d.1	$$⊢\phi \to \psi$$
Assertion	pm2.24d	$$⊢\phi \to \left(\neg \psi \to \chi \right)$$

Proof

Step	Hyp	Ref	Expression
1		pm2.24d.1	$$⊢\phi \to \psi$$
2	1	a1d	$$⊢\phi \to \left(\neg \chi \to \psi \right)$$
3	2	con1d	$$⊢\phi \to \left(\neg \psi \to \chi \right)$$