Let $(\mathbb{R}, d)$ a metric space. Let $S \subseteq \mathbb{R}$.
I know that an open ball in $S$ is not necessarily an open ball in $\mathbb{R}$, but is it a closed ball in $S$ closed in $\mathbb{R}$?
Let $(\mathbb{R}, d)$ a metric space. Let $S \subseteq \mathbb{R}$.
I know that an open ball in $S$ is not necessarily an open ball in $\mathbb{R}$, but is it a closed ball in $S$ closed in $\mathbb{R}$?
No. Consider $S = (-1,1)$. Then $\overline{B_S}(0,1) = S$ which is not closed in $\mathbb{R}$.