If you want the arctan of b/c and you want it expressed in degrees, then use atand() The result will be in the range -90 to +90. atand() cannot be used for the full 4-quadrant arctan
The normal arctan functions are atan() and atan2(), both of which return radians. atan(b/c) returns [-pi/2, pi/2] radians and atan2(b,c) returns [-pi, pi] radians.
The conversion from radians to degrees is to multiply by 180 and divide by pi. Applying that to the [-pi, pi] range would be +/- pi*(180/pi) which would be +/- 180 as you would hope for a 4-quadrant arctan. The formula you were using would be for +/- pi*(pi/90) which would be +/- pi^2/90 which would be about +/- 0.1097
It is not clear why you would multiply an angle by r, especially if r represents a radius??
Please re-check your formula as it seems likely to be wrong.
