relativeBearing=: 180 - 360 | 180 + -

tests=: _99&".;._2 noun define
20 45
-45 45
-85 90
-95 90
-45 125
-45 145
29.4803  -88.6381
-78.3251  -159.036
-70099.74233810938  29840.67437876723
-165313.6666297357  33693.9894517456
1174.8380510598456  -154146.66490124757
60175.77306795546  42213.07192354373
)