ATAN
ATAN
Section: Linux Programmer's Manual (3) Updated: 2010-09-20 Local index
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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.
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)
COLOPHON
This page is part of release 3.27 of the Linux
man-pages
project.
A description of the project,
and information about reporting bugs,
can be found at
http://www.kernel.org/doc/man-pages/.

Index
NAME
SYNOPSIS
DESCRIPTION
RETURN VALUE
ERRORS
CONFORMING TO
SEE ALSO
COLOPHON
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Time: 21:42:00 GMT, April 16, 2011