import cairo, math
var
  xc = 128.0
  yc = 128.0
  radius = 100.0
  angle1 = 45.0   PI / 180.0  # angles are specified
  angle2 = 180.0  PI / 180.0  # in radians

ctx.setLineWidth(10.0)
ctx.arc(xc, yc, radius, angle1, angle2)
ctx.stroke()

# draw helping lines
ctx.setSourceRGBA(1.0, 0.2, 0.2, 0.6)
ctx.setLineWidth(6.0)

ctx.arc(xc, yc, 10.0, 0, 2PI)
ctx.fill()

ctx.arc(xc, yc, radius, angle1, angle1)
ctx.lineTo(xc, yc)
ctx.arc(xc, yc, radius, angle2, angle2)
ctx.lineTo(xc, yc)
ctx.stroke()