ATAN
Section: Linux Programmer's Manual (3)
Updated: 2013-10-07
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NAME
atan, atanf, atanl - arc tangent function
SYNOPSIS
#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
DESCRIPTION
The
atan()
function calculates the principal value of the arc tangent of
x;
that is the value whose tangent is
x.
RETURN VALUE
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.
ERRORS
No errors occur.
ATTRIBUTES
Multithreading (see pthreads(7))
The
atan(),
atanf(),
and
atanl()
functions are thread-safe.
CONFORMING TO
C99, POSIX.1-2001.
The variant returning
double
also conforms to
SVr4, 4.3BSD, C89.
SEE ALSO
acos(3),
asin(3),
atan2(3),
carg(3),
catan(3),
cos(3),
sin(3),
tan(3)
Index
- NAME
-
- SYNOPSIS
-
- DESCRIPTION
-
- RETURN VALUE
-
- ERRORS
-
- ATTRIBUTES
-
- Multithreading (see pthreads(7))
-
- CONFORMING TO
-
- SEE ALSO
-
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