\[\boxed{\mathbf{930.}}\]
\[a = \frac{3\pi}{4}\ (рад);\ \ R = 1\ (см).\]
\[S = \frac{R^{2}}{2} \bullet a = \frac{1^{2}}{2} \bullet \frac{3\pi}{4} = \frac{3\pi}{8}\ \left( см^{2} \right).\]
\[Ответ:\ \ \frac{3\pi}{8}\ см^{2}.\]