Making Ellipses by Folding Disks

摘要

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.