Making Ellipses by Folding Disks
In an article entitled The Ellipse, Martin Gardner explains a simple way to `fold' an ellipse inside a circle. It is surprising that an ellipse appears through folding, but there are more surprises in store: For every point on the circle there is a triangle with that point as one of the vertices that both circumscribes the ellipse and is inscribed in the circle.
Gorkin, Pamela. "Making Ellipses by Folding Disks." (2021) : 53.