ГДЗ по геометрии 9 класс Мерзляк Задание 246

\[R = \frac{a}{2\ tg\frac{180{^\circ}}{3}} = \frac{a}{2\ tg\ 60{^\circ}} = \frac{a}{2\sqrt{3}}.\]

\[S = \pi R^{2} = \pi \bullet \left( \frac{a}{2\sqrt{3}} \right)^{2} = \frac{\pi a^{2}}{12}.\]

\[Ответ:\ \ \frac{\pi a^{2}}{12}.\]