Limit Points in Open Extension Space

Theorem
Let $T = \left({S, \tau}\right)$ be a topological space.

Let $T^*_{\bar p} = \left({S^*_p, \tau^*_{\bar p}}\right)$ be the open extension space of $T$.

Let $x \in S$.

Then $p$ is a limit point of $x$.

Similarly, let $U \subseteq S^*_p$.

Then $p$ is a limit point of $U$.

Proof
Every open set of $T^*_p = \left({S^*_p, \tau^*_{\bar p}}\right)$ except $S^*_p$ does not contain the point $p$ by definition.

So every open set $U \in \tau^*_{\bar p}$ such that $p \in U$ (there is only the one such open set) contains $x$.

So:
 * by definition of the limit point of a set, $p$ is a limit point of $U$, and


 * by definition of the limit point of a point, $p$ is a limit point of $x$.