On the unit circle the coordinates of P(theta) are (0.588, 0.809). Find the coordinates of P(2theta). Please help.

(0.588, 0.809).

cos(theta) = 0.588,
theta = 53.98 deg.
2theta = 2 * 53.98 = 107.98 deg.

cos107.98 = -0.309,
sin107.98 = 0.951.

(-0.309, 0.951).