1ATAN(3)                    Linux Programmer's Manual                   ATAN(3)
2
3
4

NAME

6       atan, atanf, atanl - arc tangent function
7

SYNOPSIS

9       #include <math.h>
10
11       double atan(double x);
12       float atanf(float x);
13       long double atanl( long double x);
14
15       Link with -lm.
16
17   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
18
19       atanf(), atanl():
20           _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
21               || /* Since glibc 2.19: */ _DEFAULT_SOURCE
22               || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
23

DESCRIPTION

25       These  functions calculate the principal value of the arc tangent of x;
26       that is the value whose tangent is x.
27

RETURN VALUE

29       On success, these functions return the principal value of the arc  tan‐
30       gent of x in radians; the return value is in the range [-pi/2, pi/2].
31
32       If x is a NaN, a NaN is returned.
33
34       If x is +0 (-0), +0 (-0) is returned.
35
36       If  x  is  positive  infinity  (negative  infinity),  +pi/2  (-pi/2) is
37       returned.
38

ERRORS

40       No errors occur.
41

ATTRIBUTES

43       For  an  explanation  of  the  terms  used   in   this   section,   see
44       attributes(7).
45
46       ┌─────────────────────────┬───────────────┬─────────┐
47       │Interface                │ Attribute     │ Value   │
48       ├─────────────────────────┼───────────────┼─────────┤
49       │atan(), atanf(), atanl() │ Thread safety │ MT-Safe │
50       └─────────────────────────┴───────────────┴─────────┘

CONFORMING TO

52       C99, POSIX.1-2001, POSIX.1-2008.
53
54       The variant returning double also conforms to SVr4, 4.3BSD, C89.
55

SEE ALSO

57       acos(3), asin(3), atan2(3), carg(3), catan(3), cos(3), sin(3), tan(3)
58

COLOPHON

60       This  page  is  part of release 5.02 of the Linux man-pages project.  A
61       description of the project, information about reporting bugs,  and  the
62       latest     version     of     this    page,    can    be    found    at
63       https://www.kernel.org/doc/man-pages/.
64
65
66
67                                  2017-09-15                           ATAN(3)
Impressum