What is the angle at the centre theorem
Angle at the centre is twice the angle at the circumference subtended by the same arc
What is the angle in a semicircle theorem
Angle in a semicircle is 90 degrees
What is the angles in the same segment theorem
Angles in the same segment are equal
What is the cyclic quadrilateral theorem
Opposite angles of a cyclic quadrilateral add to 180 degrees
What is the tangent and radius theorem
A tangent to a circle is perpendicular to the radius at the point of contact
What is the alternate segment theorem
Angle between tangent and chord equals angle in alternate segment
What is the angle between two tangents theorem
Angle between two tangents from a point outside the circle equals 180 minus the angle at centre
What is chord bisector theorem
A line from the centre that bisects a chord is perpendicular to the chord
What is tangent from external point theorem
Tangents from the same external point are equal in length
What is the radius perpendicular to chord theorem
The perpendicular from the centre to a chord bisects the chord
