ATAN(3) Library Functions Manual ATAN(3)

atan, atanf, atanl
arc tangent function of one variable

Math Library (libm, -lm)

#include <math.h>

double
atan(double x);

float
atanf(float x);

long double
atanl(long double x);

The atan(), atanf(), and atanl() functions compute the principal value of the arc tangent of x in the range [-pi/2, +pi/2].

acos(3), asin(3), atan2(3), cos(3), cosh(3), math(3), sin(3), sinh(3), tan(3), tanh(3)

The atan() functions conforms to ISO/IEC 9899:1999 (“ISO C99”).
January 29, 2013 NetBSD 9.0