Theorem com13

Commutation of antecedents. Swap 1st and 3rd. (Contributed by NM, 25-Apr-1994.) (Proof shortened by Wolf Lammen, 28-Jul-2012.)

Hypothesis
com3.1
\( \vdash \varphi \rightarrow \psi \rightarrow \chi \rightarrow \theta \)
Conclusion
\( \vdash \chi \rightarrow \psi \rightarrow \varphi \rightarrow \theta \)
Proof
com3.1
com3r _
com23 _