## The Lesson

A cyclic quadrilateral is a 4 sided shape where each corner touches the circle. Both pairs of opposite angles add up to 180°.## How to Use the Circle Theorem where Opposite Angles in a Cyclic Quadrilateral Add Up to 180°

## Question

What is the angle θ in the circle below?## Step-by-Step:

# 1

The opposite angles add up to 180°.

70° + θ = 180°

# 2

Subtract the known angle from 180°.

θ = 180° − 70° = 110°