Let \(M\) be a \(n\)-manifold. A subset \(U\subseteq M\) is called coordinate ball if it is homeomorphic to a ball in \(\mathbb{R}^n\).
Let \(M\) be a \(n\)-manifold. A subset \(U\subseteq M\) is called coordinate ball if it is homeomorphic to a ball in \(\mathbb{R}^n\).