The following curve is the locus of point X resulting in the classical proof of Pythagora's theorem. Usually X is defined as the intersection point of BL with the polar of L with respect to the circle with diameter AC, the hypotenuse of the right angled triangle ABC. The figure below indicates the paths described by various moving points related to the triangle as vertex B varies on the circle with diameter AC. The parameter a entering the formula is a=AC/2 and the origin is at the middle O of AC (See Pythagoras.html , Polar.html ).
Bicorn y2(a2-x2) = (x2+2ay-a2)2, parametric equations: x = asin(t), y = (acos2(t)/(2-cos(t)).