TeX Quellcode:

\begin{array}{rcl} A_O &=& 4\pi \left(\dfrac{d}{2}\right)^2 \cr A_O &=& 4\pi \cdot \left(\dfrac{6{,}7}{2} \, cm\right)^2 \cr A_O &\approx& 141{,}03 \, cm^2 \end{array}