Trisectrix of Maclaurin

Turn one line about O and another about a second point three times as fast, both starting along the line through the two points, and the point where they cross traces Maclaurin’s trisectrix. He studied it in 1742. It has a loop at O and an asymptote, and since the angle at O stays a third of the angle at the second point, it trisects any angle.

r = a sin 3θ / sin 2θ

On mathcurve.com as Trisectrice de Maclaurin