Add maths packages

sections/german/09/09.md

@@ -14,6 +14,7 @@
     <pre class="lang-tex hljs"><code>\begin{equation}
   2 \sqrt{\frac{\pi^2}{3} \cdot c_2}
 \end{equation}</code></pre>
+    <p>Pakete: <code>amsmath</code>, <code>amsthm</code>, <code>amssymb</code>, <code>mathtools</code></p>
 	</div>
 	<div class="layout-preview">
 		<img src="sections/german/09/simple-maths-crop.svg" style="max-height: 100%;">
@@ -124,5 +125,3 @@
     <p class="fragment" style="text-align: center;">$4 \cdot \left(\frac{1}{2} + 12 \cdot \left(\frac{1}{2 + 86 \cdot \left(\frac{1}{2} \right)} \right) \right)$</p>
   </div>
 </div>
-
-TODO: Was kann amsmath, was amsthm?