Theorem expcom

Description: Exportation inference with commuted antecedents. (Contributed by NM, 25-May-2005)

	Ref	Expression
Hypothesis	ex.1	$$⊢\left(\phi \wedge \psi \right)\to \chi$$
Assertion	expcom	$$⊢\psi \to \left(\phi \to \chi \right)$$

Proof

Step	Hyp	Ref	Expression
1		ex.1	$$⊢\left(\phi \wedge \psi \right)\to \chi$$
2	1	ex	$$⊢\phi \to \left(\psi \to \chi \right)$$
3	2	com12	$$⊢\psi \to \left(\phi \to \chi \right)$$