atan (3)

Leading comments

Copyright 1993 David Metcalfe (david@prism.demon.co.uk)
and Copyright 2008, Linux Foundation, written by Michael Kerrisk
    <mtk.manpages@gmail.com>

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(The comments found at the beginning of the groff file "man3/atan.3".)

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

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).

Interface	Attribute	Value
atan(), atanf(), atanl()	Thread safety	MT-Safe

CONFORMING TO

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

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