Cyclic quadrilaterals are the special group of quadrilaterals with all its base lying on the circumference of the circle. In other words, a quadrilateral inscribed in a circle is called a cyclic quadrilateral.
Cyclic quadrilateral are characterised by some special features such as
Sum of opposite angles of a cyclic quadrilateral is always a supplementary angle.
If one of the sides of a cyclic quadrilateral is produced, then the exterior angle so formed is always double of the corresponding interior angle.
Using the property 1
We find that since the quadrilateral is cyclic, opposite pairs must be supplementary
