.\"	$OpenBSD: atan2.3,v 1.19 2016/04/26 19:49:22 tb Exp $
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.\"     from: @(#)atan2.3	5.1 (Berkeley) 5/2/91
.\"
.Dd $Mdocdate: April 26 2016 $
.Dt ATAN2 3
.Os
.Sh NAME
.Nm atan2 ,
.Nm atan2f ,
.Nm atan2l
.Nd arc tangent functions of two variables
.Sh SYNOPSIS
.In math.h
.Ft double
.Fn atan2 "double y" "double x"
.Ft float
.Fn atan2f "float y" "float x"
.Ft long double
.Fn atan2l "long double y" "long double x"
.Sh DESCRIPTION
The
.Fn atan2
function computes the principal value of the arc tangent of
.Ar y/ Ns Ar x ,
using the signs of both arguments to determine the quadrant of
the return value.
The
.Fn atan2f
function is a single precision version of
.Fn atan2 .
The
.Fn atan2l
function is an extended precision version of
.Fn atan2 .
.Sh RETURN VALUES
The
.Fn atan2 ,
.Fn atan2f
and
.Fn atan2l
functions, if successful,
return the arc tangent of
.Ar y/ Ns Ar x
in the range
.Bk -words
.Bq \&- Ns pi , \&+ Ns pi
.Ek
radians.
If both
.Ar x
and
.Ar y
are zero, the global variable
.Va errno
is set to
.Er EDOM .
.Sh SEE ALSO
.Xr acos 3 ,
.Xr asin 3 ,
.Xr atan 3 ,
.Xr cos 3 ,
.Xr cosh 3 ,
.Xr sin 3 ,
.Xr sinh 3 ,
.Xr tan 3 ,
.Xr tanh 3
.Sh STANDARDS
The
.Fn atan2
function conforms to
.St -ansiC .