1. Angles in Circles Angles on the circumference Angles from a diameter
Angles at the centre & the circumference
Cyclic quadrilaterals
Tangents

2. Angles on the circumference
Angles on the circumference from opposite ends of a chord are the same

3. Angles from a diameter
Angles on the circumference from opposite ends of a diameter are 90°

4. Angles at the centre & the circumference
Angles on the circumference from opposite ends of a chord are half of the angle at the centre (from the same chord)

5. Cyclic quadrilaterals
Opposite angles of a quadrilateral on the circumference total 180°

6. Tangents
The angle between a tangent and a radius (where the tangent touches the circle) is 90°