if a cord of length L is drawn... Let D be the distance from the center of the center of the circle to the cord. let the remaining distance to the edge of the circle be h. (such that r = D + h)
To get started, i think we need to obtain the equations for D and L
let theta be the central angle.
D = r*cos(.5*theta)
D = .5*L*cot(.5*theta)
D = .5(4*r^2-L^2)^.5
L = 2*r*sin(.5*theta)
L = 2*D*tan(.5*theta)
L = 2*(r^2-D^2)^.5
L = 2*[h*(2*r-h)]^.5
now, any ideas on what comes next???