When considered as a subset of \mathbb{R}^2, \mathbb{Z} is a closed set.
Proof.
We will show, by definition, that \mathbb{Z} \subset \mathbb{R}^2 is closed.
That is, we need to show that, if n is a limit point of \mathbb{Z}, then n \in \mathbb{Z}.
I think this becomes vacuously true, since our...