Theorem simpl13

Simplification of conjunction. (Contributed by NM, 9-Mar-2012.) (Proof shortened by Wolf Lammen, 24-Jun-2022.)

Conclusion
\( \vdash ((\varphi \wedge \psi \wedge \chi) \wedge \theta \wedge \tau) \wedge \eta \rightarrow \chi \)
Proof
simpl3
3ad2antl1 _