ATAN

Section: Linux Programmer's Manual (3)
Updated: 2013-10-07
Index Return to Main Contents
 

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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Time: 02:55:18 GMT, September 18, 2014