public static bool operator ==(Angle a, Angle b)
        {
            object o1 = a;
            object o2 = b;

            if (o1 == null && o2 == null)
            {
                return(true);
            }
            if (o1 == null ^ o2 == null)
            {
                return(false);
            }
            decimal bConvertedValue = ConvertAngleValue(b.Value, b.Units, a.Units);

            return(bConvertedValue.ApproximatelyEquals(a.Value));
        }