Circle Properties & Theorems

Learn the key circle theorems — angles, chords, tangents — and how to prove and apply them.

Circle Angle Theorems

Apply the six key circle angle theorems — from the angle at the centre to angles in a cyclic quadrilateral.
Circle Vocabulary and Properties

Learn the key parts of a circle — radius, diameter, chord, arc, sector, segment, tangent — and their basic properties.
Cyclic Quadrilaterals

Identify cyclic quadrilaterals and use the opposite-angles rule to find missing angles in circle problems.