Circle Theorem 7 - Chords of a Circle
Perpendicular Line from Centre Bisects Chord
Perpendicular Line from Centre Bisects Chord
By moving points A or B you can adjust the lenght of chord AB.
D has been automatically set to the mid-point of AB.
Note that the angles ODB and ODA are right angles.
The converse is true:
The perpendicular bisector of a chord will passthrough the centre of the circle.