If A, B, C, D are the successive angles of a cyclic quadrilateral

If A, B, C, D are the successive angles of a cyclic quadrilateral, then what is cos A + cos B + cos C + cos D equal to?

1. 0
2. 1
3. 2
4. 4

Answer

In cyclic quadrilateral, sum of opposite angles is 180°. You can assume all angles to be 90°.

cos 90° = 0

The correct option is A.