code: public void arc(double centerX, double centerY,
  			double radiusX, double radiusY,
  			double startAngle, double length) {
  		this.gc.arc(
  				doc2fxX(centerX), doc2fxY(centerY),
  				doc2fxSize(radiusX), doc2fxSize(radiusY),
  				doc2fxAngle(Math.toDegrees(startAngle)), doc2fxSize(length));
  	}
docs: Adds path elements to the current path to make an arc that uses Euclidean
  degrees. This Euclidean orientation sweeps from East to North, then West,
  then South, then back to East.
  The coordinates are transformed by the current transform as they are
  added to the path and unaffected by subsequent changes to the transform.
  The current path is a path attribute
  used for any of the path methods as specified in the
  Rendering Attributes Table of {@link GraphicsContext}
  and <b>is not affected</b> by the {@link #save()} and
  {@link #restore()} operations.
  
  @param centerX the center x position of the arc.
  @param centerY the center y position of the arc.
  @param radiusX the x radius of the arc.
  @param radiusY the y radius of the arc.
  @param startAngle the starting angle of the arc in the range {@code 0-2PI}
  @param length  the length of the baseline of the arc.