TeX Quellcode:

\begin{array}{rclcl} \cos(\beta) &=& \dfrac{a}{c} & \vert & \cdot c \cr a &=& c \cdot \cos(\beta) \cr a &=& 6{,}7 \cdot \cos \left( \dfrac{3 \pi}{5} \right) \cr a & \approx & -2{,}07 \end{array}