OpenSAT

The area of a sector of a circle is given by the formula \frac{\theta}{360^{\circ}}\cdot \pi r^2, where $\theta$ is the central angle of the sector in degrees and r is the radius of the circle. Substituting $72^{\circ}$ for $\theta$ and 5 for r, we get \frac{72^{\circ}}{360^{\circ}}\cdot \pi (5)^2 = \frac{1}{5}\cdot 25\pi = 5\pi$.