If there are two triangles in a circle (both with a corner at the centre of the circle), there is a relationship between each triangles centre angle, and each triangles' chord.[br]Use the applet above to discover this relationship.
What can you say about the relationship between each triangles centre angle, and subsequent chord?
If the angles at the centre are the same, then the chord lengths will be the same.
If there are two chords of the same length in a circle, there is a relationship between the distance of the centre of those chords from the centre of the circle.[br]Use the applet above to discover this relationship.
What can you say about the relationship between the lengths of two chords and their distance from the centre of the circle?
If the chord lengths are the same, the distance to the centre of the circle will be the same.
If the shortest line is drawn from the centre of the circle to a chord in that circle, there is a relationship in the angle it meets the chord at, at the angles formed on either side at the centre, AND in the lengths of the chord on either side of the line.
What can you say about the relationship:[br]that the shortest line meets the chord?[br]the size of the angle either of the line at the centre of the circle?[br]and[br]the lengths of the chords on either side of the line?
The angle is 90.[br]The angles at the centre are the same.[br]The lengths of the chord either side are the same.
This additional line is called a perpendicular bisector, as it meets the chord at 90 degrees, and cuts both the centre angle and the chord in half.
What do you think is the significance of the point where both the perpendicular bisectors of the given chords meet?