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13 Ellipse Construction The Long axis of an Ellipse is the Major Axis.
The Short axis is the Minor Axis, Figure 1.
The foci E and F are found by striking arcs with radius equal to half the Major Axis and with center at the end of the Minor Axis.
Another method is to draw a semicircle with the Major Axis as diameter, then to draw G-H parallel to the Major Axis, and G-E and H-F parallel to the Minor Axis, as shown.
An Ellipse may also be generated by a point moving so that the sum of its distances from two points (the foci) is constant and equal to the Major Axis.
For example, in Figure 2, an Ellipse may be constructed by placing a looped string around the foci E and F, and around C, one end of the Minor Axis. and moving the pencil Point P along its maximum orbit while the string is kept taut.