Let theta be an angle such that cos(theta) = -1/9 and 0 <= theta <= 2pi.
Assume that cos(theta/2) < 0. Then if:
Terminal point of theta/2 = (a1, a2), enter a1 and a2 in that order.
\((a_1, a_2) = (-1/3, 2 \sqrt{2}/3)\)
That is wrong.
