Ответ:
\[B\left( \frac{\sqrt{3}}{2};\frac{1}{2} \right);\ \ C\left( - \frac{\sqrt{3}}{2};\ - \frac{1}{2} \right);\ \ \]
\[\alpha = 30{^\circ};\ \ \beta = 210{^\circ}.\]
\[B\left( \frac{\sqrt{3}}{2};\frac{1}{2} \right);\ \ C\left( - \frac{\sqrt{3}}{2};\ - \frac{1}{2} \right);\ \ \]
\[\alpha = 30{^\circ};\ \ \beta = 210{^\circ}.\]