public static double GetAngle(this Point point)
{
if (point.Y == 0)
{
return(point.X < 0 ? Math.PI : 0);
}
if (point.X == 0)
{
return(point.Y < 0 ? -Math.PI / 2 : Math.PI / 2);
}
return(Math.Sign(point.Y) * Math.Acos(point.X / point.GetLength()));
}
