\[1)\ \frac{1}{6}\ окружности:\]
\[a = \frac{1}{6} \bullet 360{^\circ} = 60{^\circ}.\]
\[Ответ:\ \ 60{^\circ}.\]
\[2)\ \frac{1}{10}\ окружности:\]
\[a = \frac{1}{10} \bullet 360{^\circ} = 36{^\circ}.\]
\[Ответ:\ \ 36{^\circ}.\]
\[3)\ \frac{1}{2}\ окружности:\]
\[a = \frac{1}{1} \bullet 360{^\circ} = 180{^\circ}.\]
\[Ответ:\ \ 180{^\circ}.\]
\[4)\ \frac{2}{9}\ окружности:\]
\[a = \frac{2}{9} \bullet 360{^\circ} = 80{^\circ}.\]
\[Ответ:\ \ 80{^\circ}.\]