Tangent of Ellipse

x = a cos t

y = b sin t

References

• T. H. Eagles, M.A. Constructive Geometry of Plane Curves, pp. 99-145.     

• J. Dennis Lawrence, A Catalog of Special Plane Curves, pp. 72-78. 

• 2d Curves : http://www.2dcurves.com/conicsection/conicsectione.html

• Math World : http://mathworld.wolfram.com/Ellipse.html

• Jen-Chung Chuan : http://poncelet.math.nthu.edu.tw/disk6/atcm-02/talk/ellipse.html

• Famous Curves Index : http://www-gap.dcs.st-and.ac.uk/~history/Curves/Ellipse.html