Let \(f:\Omega\to\mathbb C\) be an open mapping on an open set \(\Omega\subseteq\mathbb C\). Define \(|f|(z)=|f(z)|\).
Show that \(|f|\) cannot have a local maximum at a point of \(\Omega\).
If \(\overline\Omega\) is compact and \(f\) is continuous on \(\overline\Omega\), show that \(|f|\) attains its maximum on \(\partial\Omega\).