Paper-Folding an Ellipse
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Start with a circle drawn on paper and mark a point inside it. Fold the circle so that the circumference touches the point. Make a firm crease. Repeat, using random folds. The creases form the envelope of an ellipse.
Contributed by: Borut Levart (April 2014)
Open content licensed under CC BY-NC-SA
The locator represents the point inside the circle. You can move the locator and vary the number of creases.
 D. Wells, The Penguin Dictionary of Curious and Interesting Geometry, London: Penguin, 1991.
"Paper-Folding an Ellipse"
Wolfram Demonstrations Project
Published: April 28 2014