CYCLIC QUADRILATERAL FROM GEOGEBRA

Cyclic quadrilateral: If all the four vertices of a quadrilateral, as in the figure below, lie on a circle, then such a quadrilateral is called a cyclic quadrilateral ..

  Properties:

1) The opposite angles of a cyclic quadrilateral are supplementary 

 Or 

 The sum of either pair of opposite angles of a cyclic quadrilateral are supplementary.

 2) If one side of a cyclic quadrilateral be produced, then the exterior angle will be equal to the opposite interior angle .

3) If the sum of any pair of opposite angles of a quadrilateral is 180^0, then the quadrilateral is cyclic