Ordinate and Major Axis of Ellipse
Illustration of half of an ellipse. The square of the ordinate of a point in an ellipse is to the product of the segments of the major axis made by the ordinate as the square of b to the square of a.
G.A. Wentworth Plane And Solid Geometry (Boston: Ginn & Company, 1899) 432
Courtesy the private collection of Roy Winkelman