A chord is the line joining any 2 points on the circle.
In the figure, AB,CD,EF are chords.
The line joining the midpoint of a chord and the centre of the circle is perpendicular to the chord.
The perpendicular bisector of any chord passes through the center.
The perpendicular dropped from the centre of the circle to any chord will bisect the chord.
The mid points of all the chords of equal length will form a circle with the center same as the original circle.
Distance of the chord from the centre of the circle = root(r*r - s*s/4)