ГДЗ по геометрии 9 класс Мерзляк Задание 245

\[R = \frac{a}{2\ tg\frac{180{^\circ}}{6}} = \frac{a}{2\ tg\ 30{^\circ}} =\]

\[= \frac{a}{2}\ :\frac{1}{\sqrt{3}} = \frac{a\sqrt{3}}{2}.\]

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

\[= \pi \bullet \frac{3a^{2}}{4} = \frac{3\pi a^{2}}{4}.\]

\[Ответ:\ \ \frac{3\pi a^{2}}{4}.\]