Properties of circles

- equal chords are equidistant from the centre

- the perpendicular bisector of a chord passes through the centre

- tangents from an external point are equal in length

- the line joining an external point to the centre of the circle bisects the angle between the tangents

- angle in a semicircle is a right angle

- angle between tangent and radius of a circle is a right angle

- angle at the centre is twice the angle at the circumference

- angles in the same segment are equal

- angles in opposite segments are supplementary