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NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | ATTRIBUTES | CONFORMING TO | SEE ALSO | COLOPHON |
ATAN(3) Linux Programmer's Manual ATAN(3)
atan, atanf, atanl - arc tangent function
#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
These functions calculate the principal value of the arc tangent of
x; that is the value whose tangent is x.
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
returned.
No errors occur.
For an explanation of the terms used in this section, see
attributes(7).
┌─────────────────────────┬───────────────┬─────────┐
│Interface │ Attribute │ Value │
├─────────────────────────┼───────────────┼─────────┤
│atan(), atanf(), atanl() │ Thread safety │ MT-Safe │
└─────────────────────────┴───────────────┴─────────┘
C99, POSIX.1-2001, POSIX.1-2008.
The variant returning double also conforms to SVr4, 4.3BSD, C89.
acos(3), asin(3), atan2(3), carg(3), catan(3), cos(3), sin(3), tan(3)
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latest version of this page, can be found at
https://www.kernel.org/doc/man-pages/.
2016-03-15 ATAN(3)
Pages that refer to this page: acos(3), asin(3), atan2(3), cos(3), sin(3), tan(3)