S = \frac{π d^{2}}{4} = \frac{3, 14 \cdot 6^{2} c m^{2}}{4} = 28, 3 c m^{2}

${S = \frac{\pi d^2}{4} = \frac{3,14 \cdot 6^2\,\mathrm{cm^2}}{4} = {28,3}\,\mathrm{cm^2}}$