AutoCad 2D :: Measure Angle Between Two Lines?

Several people recommended DIMANGULAR. I have some concerns using this method because it is dependent on the precision of angular units in the drawings DIMSTYLE settings. For example, if a drawing file's DIMSTYLE has a precision set to the nearest whole decimal degree or only shows degrees and minutes but not seconds then the angle may appear at a certain angle, let's say perpendicular at 90 degrees. But in reality the angle might be slightly less than 90 degrees, if its off by a few seconds.

I learned an alternative way by selecting both lines and typing the LIST command. The Angle in XY Plane will show the measurement for each segment in bearings, not azimuths. I simply find the difference between the Angles in XY Planes for both lines to determine the angle. I have a few concerns with this method.

1. How do you add subtract bearings measured in degrees, minutes, and seconds? For example, N 76d3'18" W and N 13d56'42"E? I "think" there are websites that can do this? Can this be done directly in AutoCAD through QuickCalc or some other tool?

2. Lines, but not polylines, have Angles in XY Planes in the LIST command. Is this because AutoCAD assumes that polylines will be composed of more than one segment (and each segment with a possible different angle)? Is there anyway to measure the angle of a single one-segment polyline?

Is there a DIFFERENT way between the two methods I just described to measure the angle between two lines (and two polylines) in AutoCAD?