format updates

content/Math4121/Math4121_L24.md

@@ -14,7 +14,8 @@ $$
 
 where $\partial S$ is the boundary of $S$ and $c_e(\partial S)=0$.
 
-Example:
+<details>
+<summary>Examples for Jordan measurable</summary>
 
 1. $S=\mathbb{Q}\cap [0,1]$ is not Jordan measurable.
 
@@ -56,6 +57,8 @@ So $c_e(SVC(4))=\frac{1}{2}$.
 
 > General formula for $c_e(SVC(n))=\frac{n-3}{n-2}$, and since $SVC(n)$ is nowhere dense, $c_i(SVC(n))=0$.
 
+</details>
+
 ### Additivity of Content
 
 Recall that outer content is sub-additive. Let $S,T\subseteq \mathbb{R}^n$ be disjoint.
@@ -80,7 +83,8 @@ $$
 c(\bigcup_{i=1}^N S_i)=\sum_{i=1}^N c(S_i)
 $$
 
-Proof:
+<details>
+<summary>Proof</summary>
 
 $$
 \begin{aligned}
@@ -96,7 +100,7 @@ $$
 c(\bigcup_{i=1}^N S_i)=\sum_{i=1}^N c(S_i)
 $$
 
-QED
+</details>
 
 ##### Failure for countable additivity for Jordan content