GCSE Maths Revision Guide
Circle Theorems
The geometric laws governing angles in circles. This free GCSE Maths module combines short explanations, worked examples, flashcard-style recall, and timed practice so students can revise the topic without creating an account.
Foundation Skills
Tangent & Radius
A tangent meets a radius at exactly 90°.
Two Tangents
Two tangents from the same external point to a circle are equal in length.
Angles in a Semicircle
The angle in a semicircle is always 90°.
Higher Skills
Angles at Center/Circumference
The angle at the center is TWICE the angle at the circumference.
Cyclic Quadrilaterals
Opposite angles in a cyclic quadrilateral (all corners on the circle) add up to 180°.
Alternate Segment Theorem
The angle between a tangent and its chord is equal to the angle in the alternate segment.
Same Segment
Angles in the same segment (from the same chord) are equal.
Radius bisects Chord
A radius that is perpendicular to a chord bisects the chord (cuts it in half).