freebsd-dev/lib/msun/man/acos.3

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.\"     from: @(#)acos.3	5.1 (Berkeley) 5/2/91
.\"	$Id$
.\"
.Dd May 2, 1991
.Dt ACOS 3
.Os
.Sh NAME
.Nm acos ,
.Nm acosf
.Nd arc cosine functions
.Sh SYNOPSIS
.Fd #include <math.h>
.Ft double
.Fn acos "double x"
.Ft float
.Fn acosf "float x"
.Sh DESCRIPTION
The
.Fn acos
and the
.Fn acosf
functions compute the principal value of the arc cosine of
.Fa x .
A domain error occurs for arguments not in the range [-1, +1].
For a discussion of error due to roundoff, see
.Xr math 3 .
.Sh RETURN VALUES
The 
.Fn acos
and the
.Fn acosf
functions return the arc cosine in the range
.Bq 0 , \*(Pi
radians.
On the
.Tn VAX
and
.Tn Tahoe ,
if:
.Bd -unfilled -offset indent
.Pf \&| Ns Ar x Ns \&| > 1 ,
.Ed
.Pp
.Fn acos x
sets the global variable
.Va errno
to
.Dv EDOM
and a reserved operand fault is generated.
.Sh SEE ALSO
.Xr asin 3 ,
.Xr atan 3 ,
.Xr atan2 3 ,
.Xr cos 3 ,
.Xr cosh 3 ,
.Xr math 3 ,
.Xr sin 3 ,
.Xr sinh 3 ,
.Xr tan 3 ,
.Xr tanh 3
.Sh STANDARDS
The
.Fn acos
function conforms to
.St -ansiC .