An angle θ measures −210∘.
(a) Convert θ to radian measure, giving your answer in the interval (−π,π].
(b) Identify the quadrant in which the terminal side of θ lies.
(c) Find the exact coordinates of the point on the unit circle that corresponds to θ.
(d) Verify numerically that the coordinates found in part (c) satisfy the relation sin2θ+cos2θ=1.