Terminology
RadiusCentre to edge
Angle Notation
means the angle at vertex . When multiple angles share a vertex, use subscripts: .
Proof Writing
When you prove a statement, write the reason in brackets after each line — e.g. (∠ at centre = 2 × ∠ at circumference) or (OD ⊥ AB, given). Examiners award marks for the correct reason, not just the correct value.
Tip
Learn the name of every theorem by heart. Writing the correct answer without the correct reason costs marks in every circle geometry question.