EllipseArc angle xradius yradius startAngle
draws part of or all of an ellipse based on the turtle heading, turtle position and the given arguments.
The ellipse starts at the rear of the turtle heading and sweeps by the amount of angle starting at startAngle.
The size is based on the xradius and yradius values. The current turtle position will be at the center of the ellipse. EllipseArc will also follow wrap/fence/windows modes.
xradius is the radius from the turtle to her right till the arc.
yradius is the radius in direction of the turtle's head till the arc.
EllipseArc 360 100 200 0
EllipseArc 90 50 50 0
EllipseArc 90 50 50 90