Theorem pm3.2an3

Version of pm3.2 for a triple conjunction. (Contributed by Alan Sare, 24-Oct-2011.) (Proof shortened by Kyle Wyonch, 24-Apr-2021.) (Proof shortened by Wolf Lammen, 21-Jun-2022.)

Conclusion
\( \vdash \varphi \rightarrow \psi \rightarrow \chi \rightarrow \varphi \wedge \psi \wedge \chi \)
Proof
id
3exp _