There are 8 **circle theorems** in total, and they’re all facts about angles/lengths in particular situations all involving **circles**.

- The angle at the center is twice the angle at the circumference
- The angle in a semicircle is a right angle
- Angles in the same segment are equal
- Opposite angles in a cyclic quadrilateral sum to 180°
- The angle between the chord and the tangent is equal to the angle in the alternate segment
- The perpendicular radius to the chord bisects the chord
- The radius is perpendicular to the tangent
- The tangents from a point to a circle are equal in length