Math Problem : JJ.6 Congruent two sectors

The figure below is a graphic which overlapped sectors with 12 cm in radius and 30 degrees of central angles.

Find the area of the shadow area.

Pi is assumed to be 3.

Answer

36 cm²

Solution

Since △ABO and △CDO are congruent,　(Area of shadow area) = (figure ACDO) - (△ABO) = (figure ACDO) - (△CDO) = sector ACO = 12 × 12 × 3 × 30/360 = 36cm².