# Cyclic Quadrilateral in Circle Geometry

Cyclic Quadrilateral is inscribed into a circle, whose vertices all lie on a circle.
The properties of Cyclic Quadrilateral in Circle Geometry are;
1. Opposite angles in a cyclic quadrilateral supplementary.
2. Exterior angle and its opposite angle are equal.

### Worked Examples of Cyclic Quadrilateral

(a)    Prove that $FADG$ is a cyclic quadrilateral.

(b)    Prove that $GA$ is a tangent to the circle through $A$, $B$, $C$ and $D$.