I use autocad, if I extrapolate a given "angle" over a distance, the variance grows.
I prefer to measure all my angles, compound or otherwise... it's much more accurate.
like this OP:
a=0(anchor point)
b=x
c=y
you measure the distance to B from 0, then you measure the distance to C from 0 then you measure the distance between B and C and that gives you an EXACT angle that is repeatable with great accuracy. this can be done anywhere along the X/Y axis, though it is always more accurate to measure as far away from 0 as possible to avoid multiplying an error.
if X/Y are not level/square in both directions, then you need to also add those measurements of offset from level/square to your work.
For me, the expression "angle" is nothing more than the sum of these measurements stated above... better to use that sum than some other form of expression (angle) if accuracy is the goal.
FWIW... I digitize to the ten-thousandths... certainly much more critical than some bulbous building or structure.
But do what you want.