ATAN(3) BSD Programmer's Manual ATAN(3)
atan, atanf - arc tangent function of one variable
libm
#include <math.h> double atan(double x); float atanf(float x);
The atan() and atanf() 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 ANSI X3.159-1989 ("ANSI C89"). MirBSD #10-current May 2, 1991 1