xc = 0.5
yc = 0.5
radius = 0.4
angle1 = 45.0  * (M_PI/180.0)  #/* angles are specified */
angle2 = 180.0 * (M_PI/180.0)  #/* in radians           */

snippet_normalize (cr, width, height)

cr.arc (xc, yc, radius, angle1, angle2)
cr.stroke ()

#/* draw helping lines */
cr.set_source_rgba (1,0.2,0.2,0.6)
cr.arc (xc, yc, 0.05, 0, 2*M_PI)
cr.fill ()
cr.set_line_width (0.03)
cr.arc (xc, yc, radius, angle1, angle1)
cr.line_to (xc, yc)
cr.arc (xc, yc, radius, angle2, angle2)
cr.line_to (xc, yc)
cr.stroke ()