Cornoid

Where a horizontal line cuts a circle at P and P′, drop a perpendicular from P to the line through P′ parallel to OP: its foot is a point of the cornoid. Alberto Sanchez studied it in 1895. It is also the orthoptic of the curve mathcurve calls the Maltese cross.

x = a cos t (1 - 2 sin² t), y = a sin t (1 + 2 cos² t)

On mathcurve.com as Cornoïde