updates

content/Math4201/Math4201_L4.md

@@ -115,7 +115,7 @@ An open set with respect to $\mathcal{T}_{\mathcal{S}}$ is a subset of $X$ such
 
 <details>
 
-<summary>Example (standard topology on $\mathbb{R}$)</summary>
+<summary>Example (standard topology on real numbers)</summary>
 
 Let $X=\mathbb{R}$. Take $\mathcal{S}=\{(-\infty, a)|a\in \mathbb{R}\}\cup \{(a,+\infty)|a\in \mathbb{R}\}$.