The Circular Tractrix
W. G. Cady · American Mathematical Monthly · 1965
After a historical sketch the equations are derived for tractrix curves whose directrix is a circle. Two types are distinguished. In one, the curve has the form of a spiral. In the other, there is a succession of cusps forming a flower-like pattern; the conditions are considered under which the curve can close upon itself. A mechanical device for drawing the curves is described.