1. Circle Radius Diameter Tangent Circumference

2. Angles subtended by the same chord are equal Chord

3. Angle subtended by the same chord at the centre is twice that at the circumference 2a a

4. Angle subtended by the same chord at the centre is twice that at the circumference 25 ○ What is the value of angle a? a a 50 ○ 2a = 180 ○ – 50 ○ 2a = 130 ○ a = 65 ○

5. Cyclic Quadrilaterals

6. The opposite angles of a cyclic quadrilateral add up to 180 ○ A cyclic quadrilateral is a quadrilateral whose vertices all lie on the circumference of a circle. a b Angle a + angle b = 1 80 ○

7. Angle in a semi circle equal 90 ○

8. Radius and Tangent 90\

9. The radius and tangent are at right angles o

10. Tangents to a Circle

11. Two tangents from the same point to a circle are equal

12. CIRCLES THE END THE END