Theorem pm3.42

Description: Theorem *3.42 of WhiteheadRussell p. 113. (Contributed by NM, 3-Jan-2005)

	Ref	Expression
Assertion	pm3.42	$$⊢\left(\psi \to \chi \right)\to \left(\left(\phi \wedge \psi \right)\to \chi \right)$$

Proof

Step	Hyp	Ref	Expression
1		simpr	$$⊢\left(\phi \wedge \psi \right)\to \psi$$
2	1	imim1i	$$⊢\left(\psi \to \chi \right)\to \left(\left(\phi \wedge \psi \right)\to \chi \right)$$