/// <summary>
/// Converts the angle of the line to Arithmetic Rotation.
/// </summary>
/// <param name="source">The source.</param>
/// <returns>Returns a <see cref="double" /> representing the angle.</returns>
public static double GetArithmeticAngle(this IPolyline source)
{
if (source == null)
{
return(0);
}
ILine line = new LineClass();
line.PutCoords(source.FromPoint, source.ToPoint);
return(line.GetArithmeticAngle());
}