atanl(3) Linux Man Page - System Grab Bag

Name

atan, atanf, atanl - arc tangent function

Library

Math library ( libm ", " -lm )

Synopsis

#include <math.h> 
double atan(double  x );
float atanf(float  x );
long double atanl(long double  x );

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 <= 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 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

For an explanation of the terms used in this section, see attributes(7). allbox; lbx lb lb T{ atan()atanf()atanl()

Interface	Attribute	Value
T}	Thread safety	MT-Safe

Standards

C11, POSIX.1-2008.

History

C99, POSIX.1-2001.

The variant returning double also conforms to SVr4, 4.3BSD, C89.