Tractrix

Description

Tractrix is the curve along which an object moves, under the influence of friction, when pulled on a horizontal plane by a line segment attached to a tractor (pulling) point that moves at a right angle to the initial line between the object and the puller at an infinitesimal speed. It is therefore a curve of pursuit. The tractrix has the property that the segment of its tangent, between the asymptote and the point of tangency, has constant length a.