xref: /openbsd-src/lib/libm/man/atan2.3 (revision 1c7c1e02dc27bdb87a106695fcd64d107e077f53)

.\"	$OpenBSD: atan2.3,v 1.20 2021/06/29 14:47:33 schwarze Exp $
.\" Copyright (c) 1991 The Regents of the University of California.
.\" All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\"    notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\"    notice, this list of conditions and the following disclaimer in the
.\"    documentation and/or other materials provided with the distribution.
.\" 3. Neither the name of the University nor the names of its contributors
.\"    may be used to endorse or promote products derived from this software
.\"    without specific prior written permission.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.\"     from: @(#)atan2.3	5.1 (Berkeley) 5/2/91
.\"
.Dd $Mdocdate: June 29 2021 $
.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
.Fa y Ns / Ns Fa 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
.Fa y Ns / Ns Fa x
in the range
.Bk -words
.Bq \&- Ns pi , \&+ Ns pi
.Ek
radians.
If both
.Fa x
and
.Fa 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 .