cochleoid

thumb|upright=1.25|r=\frac{\sin \theta}{\theta}, -20 thumb|upright=1.25|cochleoid (solid) and its polar inverse (dashed) thumb|upright=1.25|A flexible pole is fixed upright at one end and bent over to always form a circular arc. The other end then traces out a Cochleoid.

In geometry, a cochleoid is a snail-shaped curve similar to a strophoid which can be represented by the polar equation r=\frac{a \sin \theta}{\theta}, the Cartesian equation (x^2+y^2)\arctan\frac{y}{x}=ay, or the parametric equations x=\frac{a\sin t\cos t}{t}, \quad y=\frac{a\sin^2 t}{t}.