This paper mainly discusses how the radius of curvature of two points on the long axis of an ellipse can be expressed as AB/[(A 2 * Sint 2+B 2 * Cost 2) (3/2)] with the semi-long axis A and semi-short axis B of the ellipse.

X = cost

y=bsint

Kmax=a/b^2

Kmin=b/a^2