B rotates about the fixed A. BC = BD = x, and BF = FG = GE = EB. All links being of fixed length. Point G traces an ellipse. Remarkably it does not depend on the particular length of link x. It does depend on the relative positions of A (center of circle), E (point on BC) and H (controlling the radius of the circle). (Artobolevsky bd. II, p. 558)