Show approximation of circles and ellipses

[mgeier]

(non-rational) Polynomial curves cannot exactly represent circles and ellipses, but they can be used to approximate them:
https://en.wikipedia.org/wiki/Composite_B%C3%A9zier_curve#Approximating_circular_arcs

http://spencermortensen.com/articles/bezier-circle/

https://www.tinaja.com/glib/ellipse4.pdf

See also Salomon, David; Curves and Surfaces for Computer Graphics; 2007; appendix B.