atan(3) — Linux manual page


ATAN(3)                   Linux Programmer's Manual                  ATAN(3)

NAME         top

       atan, atanf, atanl - arc tangent function

SYNOPSIS         top

       #include <math.h>

       double atan(double x);
       float atanf(float x);
       long double atanl( long double x);

       Link with -lm.

   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

       atanf(), atanl():
           _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
               || /* Since glibc 2.19: */ _DEFAULT_SOURCE
               || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE

DESCRIPTION         top

       These functions calculate the principal value of the arc tangent of
       x; that is the value whose tangent is x.

RETURN VALUE         top

       On success, these functions return the principal value of the arc
       tangent of x in radians; the return value is in the range
       [-pi/2, pi/2].

       If x is a NaN, a NaN is returned.

       If x is +0 (-0), +0 (-0) is returned.

       If x is positive infinity (negative infinity), +pi/2 (-pi/2) is

ERRORS         top

       No errors occur.

ATTRIBUTES         top

       For an explanation of the terms used in this section, see

       │Interface                Attribute     Value   │
       │atan(), atanf(), atanl() │ Thread safety │ MT-Safe │

CONFORMING TO         top

       C99, POSIX.1-2001, POSIX.1-2008.

       The variant returning double also conforms to SVr4, 4.3BSD, C89.

SEE ALSO         top

       acos(3), asin(3), atan2(3), carg(3), catan(3), cos(3), sin(3), tan(3)

COLOPHON         top

       This page is part of release 5.08 of the Linux man-pages project.  A
       description of the project, information about reporting bugs, and the
       latest version of this page, can be found at

                                 2017-09-15                          ATAN(3)

Pages that refer to this page: acos(3)acosf(3)acosl(3)asin(3)asinf(3)asinl(3)atan2(3)atan2f(3)atan2l(3)cos(3)cosf(3)cosl(3)sin(3)sinf(3)sinl(3)tan(3)tanf(3)tanl(3)