cc [ flag ... ] file ... -lm [ library ... ] #include <math.h>
The atan() function computes the principal value of the arc tangent of x.
Upon successful completion, atan() returns the arc tangent of x in the range [-pi/2,pi/2] radians.
If x is NaN, NaN is returned.
If x is +-Inf, +-pi/2 is returned.
No errors will occur.
See attributes(5) for descriptions of the following attributes:
atan2(3M), isnan(3M), tan(3M), attributes(5)
