Poinsot's spirals

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.

Examples of the two types of Poinsot's spirals

The Poinsot spiral r=csch(θ/3).

The Poinsot spiral r=sech(θ/3).

See also

• Cotes's spiral

References

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