IMO 1985 LL CAN12

Origin: CAN

Problem

Find the maximum value of sin2 \theta1 + sin2 \theta2 + \cdot \cdot \cdot + sin2 \thetan subject to the restrictions 0 \leq\thetai \leq\pi, \theta1 + \theta2 + \cdot \cdot \cdot + \thetan = \pi.