.\" Copyright (c) 1991 The Regents of the University of California.
.\" All rights reserved.
.\"
.\" %sccs.include.redist.man%
.\"
.\"     @(#)atan.3	5.1 (Berkeley) 05/02/91
.\"
.Dd 
.Dt ATAN 3
.Os
.Sh NAME
.Nm atan
.Nd arc tangent function of one variable
.Sh SYNOPSIS
.Fd #include <math.h>
.Ft double
.Fn atan "double x"
.Sh DESCRIPTION
The
.Fn atan
function computes the principal value of the arc tangent of
.Fa x .
For a discussion of error due to roundoff, see
.Xr math 3 .
.Sh RETURN VALUES
The
.Fn atan
function returns the arc tangent in the range
.Bk -words
.Bq -\*(Pi/2 , +\*(Pi/2
.Ek
radians.
.Sh SEE ALSO
.Xr acos 3 ,
.Xr asin 3 ,
.Xr atan2 3 ,
.Xr cos 3 ,
.Xr cosh 3 ,
.Xr sin 3 ,
.Xr sinh 3 ,
.Xr tan 3 ,
.Xr tanh 3 ,
.Xr math 3 ,
.Sh STANDARDS
The
.Fn atan
function conforms to
.St -ansiC .