ATAN(3) manual page
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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():
_BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 600 || _ISOC99_SOURCE
|| _POSIX_C_SOURCE >= 200112L;
or cc -std=c99
The atan() function calculates 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.
The atan(), atanf(), and
atanl() functions are thread-safe.
C99, POSIX.1-2001. 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)
This page is
part of release 3.78 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 http://www.kernel.org/doc/man-pages/.
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