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# 18: The Catenary

If a flexible chain or rope is loosely hung between two fixed points, it hangs in a curve that looks a little like a parabola, but in fact is not quite a parabola; it is a curve called a catenary, which is a word derived from the Latin catena, a chain.

Thumbnail: The Saint Louis arch is a weighted catenary—its legs are wider than its upper section. Image used with permission (CC BY 2.0;  Bev Sykes).