GB-42-01-001 · Angles at centre and circumference

Diagram not accurately drawn

A and C lie on a circle with centre O. B is on the major arc AC. Angle ABC is 36°. Find the minor angle AOC. Give a reason.

Circle Theorems: Angle at the Centre Booklet p. 85 & p. 86

Method

Write each calculation beside the geometric reason that justifies it

Worked Example (GB-42-01-001)

Maths	Reason
$\angle AOC=2(36)=72^\circ$	Angle at the centre is twice the angle at the circumference on the same arc.

Ans = 72°