Exercise 5, § 7

Let $X, Y$ be two topological spaces, $G$ the graph in $X \times Y$ of a mapping $f : X \to Y$. Show that for each $x \in X$ the set of cluster points of $f$ at $x$ is the section $\overline{G}(x)$ of $\overline{G}$ (the closure of $G$ in $X \times Y$) at $x$.