class Magick::RVG::Utility::GraphicContext

def rotate(degrees)
  degrees = Magick::RVG.convert_one_to_float(degrees)
  @gc.rotate(degrees)
  @sx =  Math.cos(GraphicContext.degrees_to_radians(degrees))
  @rx =  Math.sin(GraphicContext.degrees_to_radians(degrees))
  @ry = -Math.sin(GraphicContext.degrees_to_radians(degrees))
  @sy =  Math.cos(GraphicContext.degrees_to_radians(degrees))
  concat_matrix
  nil
end