Circle Theorems Revision Videos

You'll want to know all the neat rules that apply to circles. We call them 'theorems'. There's lots to learn, so don't mess around searching from one place to the next. We have all the videos you need right here.

Circles are 360° of fun

Hegarty Maths covers most of what you need to know on the topic of Circle Theorems.

Two radii make an isosceles triangle

Quick video from Ron Barrow showing how two radii will always create an isosceles triangle.

Proofs

You may be asked to prove that a circle theorem is true. These videos from Miss Brooks Maths show you how to do it.

Perpendicular from the centre to a chord bisects the chord

Alternate segment theorem

Tangents from an external point are equal in length

Tangent at any point on a circle is perpendicular to the radius at that point

Opposite angles in a cyclic quadrilateral sum to 180°

Angles in the same segment are equal

Angle subtended by an arc at the centre is equal to twice the angle subtended at any point on the circumference

Angle subtended at the circumference by a semicircle is 90°