# Cyclic Polygon

A polygon whose vertices lie on a circle. Also known as an inscribed polygon.

### Cyclic Quadrilateral

A four sided polygon where the vertices ABCD lie on the circle.

In a quadrilateral inscribed in a circle the opposite angles ABC and ADC add up to 180°.

This is also true for the other pair of opposite angles.

a + c = 180°

b + d = 180°.

**Subjects: ** Geometry