/// <summary>Draw an arrow on the specified graphics context</summary>
/// <param name="context">The graphics context to draw on</param>
/// <param name="start">The start point of the arrow</param>
/// <param name="end">The end point of the arrow</param>
private static void DrawArrow(IDrawContext context, Point start, Point end)
{
double angle = Math.Atan2(end.Y - start.Y, end.X - start.X) + Math.PI;
double arrowLenght = 10;
double arrowDegrees = 10;
double x1 = start.X + arrowLenght * Math.Cos(angle - arrowDegrees);
double y1 = start.Y + arrowLenght * Math.Sin(angle - arrowDegrees);
double x2 = start.X + arrowLenght * Math.Cos(angle + arrowDegrees);
double y2 = start.Y + arrowLenght * Math.Sin(angle + arrowDegrees);
context.NewPath();
context.MoveTo(x1, y1);
context.LineTo(x2, y2);
context.LineTo(end.X, end.Y);
context.LineTo(x1, y1);
context.StrokePreserve();
context.Fill();
}