Ellipsenkonstruktion von Albrecht Dürer (1525) No 2
Change the position of the ellipse with the two smaller red points.
Move the bigger red point to generate the ellipse.
Corresponding applet see
https://www.geogebra.org/m/UspVxPyp
Explanation see
https://pavlopoulos.wordpress.com/2009/07/27/albrecht-duerers-eyer-lini/