Theorem 2a1dd

Double deduction introducing two antecedents. Two applications of 2a1dd. Deduction associated with 2a1d. Double deduction associated with 2a1 and 2a1i. (Contributed by Jeff Hankins, 5-Aug-2009.)

Hypothesis
2a1dd.1
\( \vdash \varphi \rightarrow \psi \rightarrow \chi \)
Conclusion
\( \vdash \varphi \rightarrow \psi \rightarrow \theta \rightarrow \tau \rightarrow \chi \)
Proof
2a1dd.1
a1dd _
a1dd _