Circle Theorems

A Tangent and a Radius meet at 90^o

The Perpendicular Bisector of a Chord passes through the Centre of the Circle

The Angle at the Centre of a Circle is twice the Circumference

The angle in a Semicircle is 90^o

Angles in the same Segment are Equal

Opposite Angles in a Cyclic Quadrilateral add up to 180^o

Tangents from the same point are the same Length

The Alternate Segment Theorem:

The Angle between a Tangent and a Chord is always Equal