This video was made based on the design numbered as 990 in volume 2, Mechanisms in modern technic, I. Artobolevski.
AC = a
AK – KC = b
KC = KD = (a – b)/2
Center of green slider traces an ellipse.
Traced ellipse equation:
(x.x)/(a.a) + (y.y)/(b.b) = 1