Prove the formula A = 1 2 ?r2???? for the area of a sector of a circle with radius r and central angle ????. Hint: Assume 0 < ???? < ???? 2 and place the center of the circle at the origin so it has the equation x2 + y2 = r2. Then A is the sum of the area of the triangle POQ and the area of the region PQR in the figure below.