\[
\boxed{
\begin{array}{ll}
(a) & x = 0, \; y = 1 \\
(b) & x = 0, \; y = -1 \\
(c) & x = \frac{1}{2}, \; y = \frac{\sqrt{3}}{2} \\
(d) & x = \frac{1}{2}, \; y = -\frac{\sqrt{3}}{2} \\
(e) & x = -\frac{\sqrt{2}}{2}, \; y = \frac{\sqrt{2}}{2} \\
(f) & x = -\frac{\sqrt{2}}{2}, \; y = -\frac{\sqrt{2}}{2} \\
\end{array}
}
\]