atan(), atanf() - arc tangent function of one variable
#include <math.h>
double atan (double x)
float atanf (float x)
The atan(3) and atanf(3) functions compute the principal value of the arc tangent of x.
The atanf(3) is nearly identical, except that it deals with float types rather than double.
The atan(3) and atanf(3) functions return the arc tangent in the range [--.n/2, +-.n/2] radians. If x is 0, the functions return 0.
The atan(3) and atanf(3) functions can fail for the following reasons:
acos(3)
asin(3)
atan2(3)
cos(3)
cosh(3)
sin(3)
sinh(3)
tan(3)
tanh(3)
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