Theorem a1i13

Add two antecedents to a wff. (Contributed by Jeff Hankins, 4-Aug-2009.)

Hypothesis
a1i13.1
\( \vdash \psi \rightarrow \theta \)
Conclusion
\( \vdash \varphi \rightarrow \psi \rightarrow \chi \rightarrow \theta \)
Proof
a1i13.1
a1d _
a1i _