1.\" Copyright (c) 1991 The Regents of the University of California. 2.\" All rights reserved. 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice, this list of conditions and the following disclaimer. 9.\" 2. Redistributions in binary form must reproduce the above copyright 10.\" notice, this list of conditions and the following disclaimer in the 11.\" documentation and/or other materials provided with the distribution. 12.\" 3. Neither the name of the University nor the names of its contributors 13.\" may be used to endorse or promote products derived from this software 14.\" without specific prior written permission. 15.\" 16.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 17.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 19.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 20.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 21.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 22.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 23.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 24.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 25.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26.\" SUCH DAMAGE. 27.\" 28.Dd July 31, 2008 29.Dt ACOS 3 30.Os 31.Sh NAME 32.Nm acos , 33.Nm acosf , 34.Nm acosl 35.Nd arc cosine functions 36.Sh LIBRARY 37.Lb libm 38.Sh SYNOPSIS 39.In math.h 40.Ft double 41.Fn acos "double x" 42.Ft float 43.Fn acosf "float x" 44.Ft long double 45.Fn acosl "long double x" 46.Sh DESCRIPTION 47The 48.Fn acos , 49.Fn acosf , 50and 51.Fn acosl 52functions compute the principal value of the arc cosine of 53.Fa x . 54.Sh RETURN VALUES 55These functions return the arc cosine in the range 56.Bq 0 , \*(Pi 57radians. 58If: 59.Bd -unfilled -offset indent 60.Pf \&| Ns Fa x Ns \&| > 1 , 61.Ed 62.Pp 63.Fn acos x 64raises an invalid exception and returns an \*(Na. 65.Sh SEE ALSO 66.Xr asin 3 , 67.Xr atan 3 , 68.Xr atan2 3 , 69.Xr cos 3 , 70.Xr cosh 3 , 71.Xr fenv 3 , 72.Xr math 3 , 73.Xr sin 3 , 74.Xr sinh 3 , 75.Xr tan 3 , 76.Xr tanh 3 77.Sh STANDARDS 78The 79.Fn acos , 80.Fn acosf , 81and 82.Fn acosl 83functions conform to 84.St -isoC-99 . 85