ELLIPSE will plot all or part of a parametric ellipse of the form,
(x,y) = (maj*cos(t), min*sin(t))where maj and min are the major and minor ellipse axes, respectively and where t is the parametric angle specification. Part of the ellipse can be plotted by specifying only part of the range of t. The major axis center line is offset by the angle am. The angles ast and aend define the starting and ending angles for t. Note that aend should be greater than ast. The ellipse is approximated by short, straight line segments. The number and length of the segments depend on the size of the ellipse.
CALL ELLIPSE (x,y,maj,min,am,ast,aend)
x,y (R): center of ellipse (halfway between foci)
maj (R): length of semi-major axis (distance between center and
curve through one focus)
min (R): length of minor axis (distance between center and
curve perpendicular to semi-major axis)
am (R): angle of semi-major axis from horizontal
(deg counter-clockwise)
ast (R): start angle of curve from semi-major axis
(deg counter-clockwise)
aend (R): end angle of curve from semi-major axis
(deg counter-clockwise) note: aend > ast