Quote:
Originally posted by RebAl
If you take a slinkey and hold it in two hands it makes a parabola, just a thought
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Actually, a slinky (or rope or chain) held freely will appear to take the shape of a parabola, but it is really a catenary which comes from the hyperbolic cosine function: f(x) = a cosh(x/a).
The St. Louis Arch is an example of an "upside down" catenary.
You gotta love math...