Finding the angle between two bearings is often confusing.[1]



Task

Find the angle which is the result of the subtraction b2 - b1, where b1 and b2 are the bearings.


Input bearings are expressed in the range   -180   to   +180   degrees.

The  result  is also expressed in the range   -180   to   +180   degrees.



Compute the angle for the following pairs:

 20 degrees (b1) and 45 degrees (b2)
 -45 and 45
 -85 and 90
 -95 and 90
 -45 and 125
 -45 and 145
 29.4803 and -88.6381
 -78.3251 and -159.036


Optional extra
 
Allow the input bearings to be any (finite) value.



Test cases

 -70099.74233810938 and 29840.67437876723
 -165313.6666297357 and 33693.9894517456
 1174.8380510598456 and -154146.66490124757
 60175.77306795546 and 42213.07192354373


SUB getDifference (b1!, b2!)
    r! = (b2 - b1) MOD 360!
    IF r >= 180! THEN r = r - 360!
    PRINT USING "#######.######    #######.######    #######.######"; b1; b2; r
END SUB
 
PRINT "     Bearing 1         Bearing 2        Difference"
CALL getDifference(20!, 45!)
CALL getDifference(-45!, 45!)
CALL getDifference(-85!, 90!)
CALL getDifference(-95!, 90!)
CALL getDifference(-45!, 125!)
CALL getDifference(-45!, 145!)
CALL getDifference(-45!, 125!)
CALL getDifference(-45!, 145!)
CALL getDifference(29.4803, -88.6381)
CALL getDifference(-78.3251, -159.036)
CALL getDifference(-70099.74233810938#, 29840.67437876723#)
CALL getDifference(-165313.6666297357#, 33693.9894517456#)
CALL getDifference(1174.838051059846#, -154146.6649012476#)