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ATAN
Linux Programmer's Manual (3)
20131007
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 threadsafe.
CONFORMING TO
C99, POSIX.12001.
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 3.66 of the Linux
manpages
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/manpages/.
Index
 NAME

 SYNOPSIS

 DESCRIPTION

 RETURN VALUE

 ERRORS

 ATTRIBUTES

 Multithreading (see pthreads(7))

 CONFORMING TO

 SEE ALSO

 COLOPHON

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