A **cyclic quadrilateral** is a quadrilateral inscribed in a circle. A polygon that is inscribed in a circle is a polygon whose vertices are on the circle. Some of the inscribed polygons are shown in the next figure.

In this post, we are going to show a special property of one inscribed polygon which is the cyclic quadrilateral theorem about angles. We are going to prove that its opposite angles add up to $latex 180 ^\circ$

**Theorem**

The sum of the measures of the opposite angle of a cyclic quadrilateral is $latex 180 ^\circ$ Continue reading