\[S_{с} = \frac{5}{8}S_{кр}:\]
\[S_{с} = \frac{aS_{кр}}{360{^\circ}}\ \ \]
\[a = \frac{360{^\circ} \bullet S_{с}}{S_{кр}}\]
\[a = \frac{5}{8} \bullet 360{^\circ} = 225{^\circ}.\]
\[Ответ:\ \ 225{^\circ}.\]