Ответ:
\[B\left( \frac{\sqrt{2}}{2};\frac{\sqrt{2}}{2} \right);\ \ C\left( - \frac{\sqrt{2}}{2};\frac{\sqrt{2}}{2} \right);\ \ \]
\[\alpha = \frac{\pi}{4};\ \ \beta = \frac{3\pi}{4}.\]
\[B\left( \frac{\sqrt{2}}{2};\frac{\sqrt{2}}{2} \right);\ \ C\left( - \frac{\sqrt{2}}{2};\frac{\sqrt{2}}{2} \right);\ \ \]
\[\alpha = \frac{\pi}{4};\ \ \beta = \frac{3\pi}{4}.\]