http://www.uwgb.edu/dutchs/MATHALGO/Ellipses.HTM Constructing Ellipses https://www.uwgb.edu/dutchs/MATHALGO/Ellipses.HTM University of Wisconsin; Constructing Ellipses; Steven Dutch http://www.uwgb.edu/dutchs/MATHALGO/Ellipses.HTM