Poinsot's spirals
In mathematics, Poinsot's spirals are two spirals represented by the polar equations r = a csch ( n θ ) {\displaystyle r=a\ \operatorname {csch} (n\theta )} r = a sech ( n θ ) {\displaystyle r=a\ \operatorname {sech} (n\theta )} where csch is the hyperbolic cosecant, and sech is the hyperbolic secant. They are named after the French mathematician Louis Poinsot.