?A: 0°
?B: 0°
?C: 0°
?D: 0°
Sum: 0°
Sum: 0°
Move points A, B, C, and D around the circle to create a cyclic quadrilateral. The angles inside the quadrilateral will change as you move the points, but the sum of each pair of opposite angles, A + C and B + D, will always be 180°. You may use your calculator and the angles displayed to check the sums.