Manpage of ATAN

ATAN

Section: Linux Programmer's Manual (3)
Updated: 2016-03-15
Index
 

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():

_ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
    || /* Since glibc 2.19: */ _DEFAULT_SOURCE
    || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
 

DESCRIPTION

These functions calculate 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 xin radians; the return value is in the range [-pi/2, pi/2].

If xis a NaN, a NaN is returned.

If xis +0 (-0), +0 (-0) is returned.

If xis positive infinity (negative infinity), +pi/2 (-pi/2) is returned.  

ERRORS

No errors occur.  

ATTRIBUTES

For an explanation of the terms used in this section, see attributes(7).
InterfaceAttributeValue
atan(), atanf(), atanl() Thread safetyMT-Safe
 

CONFORMING TO

C99, POSIX.1-2001, POSIX.1-2008.

The variant returning doublealso 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
CONFORMING TO
SEE ALSO

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