void ucircle (xpos, ypos, radius, theta1, theta2) CIRCLES.C Level 3
 
double xpos, ypos Coordinates of the center of the circle in user units (units on plot).
double radius Radius of the circle in x user units.
double theta1, theta2 The ends of the desired arc of the circle in radians.
 
ucircle() is used to draw an arc of a circle in user units.