Theorem in2

Description: The virtual deduction introduction rule of converting the end virtual hypothesis of 2 virtual hypotheses into an antecedent. (Contributed by Alan Sare, 21-Apr-2011) (Proof modification is discouraged.) (New usage is discouraged.)

	Ref	Expression
Hypothesis	in2.1	$$⊢\left(\phi ,\psi \to \chi \right)$$
Assertion	in2	$$⊢\left(\phi \to \left(\psi \to \chi \right)\right)$$

Proof

Step	Hyp	Ref	Expression
1		in2.1	$$⊢\left(\phi ,\psi \to \chi \right)$$
2	1	dfvd2i	$$⊢\phi \to \left(\psi \to \chi \right)$$
3	2	dfvd1ir	$$⊢\left(\phi \to \left(\psi \to \chi \right)\right)$$