TeX Quellcode:
\begin{array}{rclcl} \tan(\beta) &=& \dfrac{b}{a} & \vert & \cdot a \cr a \cdot \tan(\beta) &=& b & \vert & : \tan(\beta) \cr a &=& \dfrac{b}{\tan(\beta)} \cr a &=& \dfrac{12}{\tan\left(\dfrac{\pi}{6}\right)} \cr a &=& 12\sqrt{3} \, cm \approx 20{,}78 \, cm \end{array}