Ellipse Construction via Parallelogram Method:

Given the main axis AB and the minor axis CD. Construct the circumscribing parallelogram. Divide OA and AE into the similar number of equal parts and number the division points from A. From C, sketch a line via point 3 on time AE, and from D, draw a line via point 3 on line AO.

The point of intersection of these lines is on the desired ellipse. Correspondingly, the intersections of lines from C and D via points 1 and 2 are on the ellipse. A same construction will situate points in the other three quadrants of the ellipse. The smooth curve is to be drawn via these points to sketch the ellipse.