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In mathematics, Poinsot's spirals are two spirals represented by the polar equations

$$r = a\ \operatorname{csch} (n\theta)$$
$$r = a\ \operatorname{sech} (n\theta)$$

where csch is the hyperbolic cosecant, and sech is the hyperbolic secant.[1] They are named after the French mathematician Louis Poinsot.

Cotes's spiral

References

Lawrence, J. Dennis (1972). A Catalog of Special Plane Curves. New York: Dover. pp. 192–194. ISBN 0486602885.

Mathematics Encyclopedia