1.\" $OpenBSD: acosh.3,v 1.11 2007/05/31 19:19:35 jmc Exp $ 2.\" Copyright (c) 1991 Regents of the University of California. 3.\" All rights reserved. 4.\" 5.\" Redistribution and use in source and binary forms, with or without 6.\" modification, are permitted provided that the following conditions 7.\" are met: 8.\" 1. Redistributions of source code must retain the above copyright 9.\" notice, this list of conditions and the following disclaimer. 10.\" 2. Redistributions in binary form must reproduce the above copyright 11.\" notice, this list of conditions and the following disclaimer in the 12.\" documentation and/or other materials provided with the distribution. 13.\" 3. Neither the name of the University nor the names of its contributors 14.\" may be used to endorse or promote products derived from this software 15.\" without specific prior written permission. 16.\" 17.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 18.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 19.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 20.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 21.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 22.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 23.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 24.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 25.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 26.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 27.\" SUCH DAMAGE. 28.\" 29.\" from: @(#)acosh.3 5.2 (Berkeley) 5/6/91 30.\" 31.Dd $Mdocdate: May 31 2007 $ 32.Dt ACOSH 3 33.Os 34.Sh NAME 35.Nm acosh , 36.Nm acoshf 37.Nd inverse hyperbolic cosine functions 38.Sh SYNOPSIS 39.Fd #include <math.h> 40.Ft double 41.Fn acosh "double x" 42.Ft float 43.Fn acoshf "float x" 44.Sh DESCRIPTION 45The 46.Fn acosh 47function computes the inverse hyperbolic cosine 48of the real 49argument 50.Ar x . 51The 52.Fn acoshf 53function is a single precision version of 54.Fn acosh . 55.Sh RETURN VALUES 56If x is less than one, 57.Fn acosh "x" 58and 59.Fn acoshf "x" 60return NaN and set the global variable 61.Va errno 62to EDOM. 63.Sh SEE ALSO 64.Xr asinh 3 , 65.Xr atanh 3 , 66.Xr exp 3 , 67.Xr infnan 3 , 68.Xr math 3 69.Sh HISTORY 70The 71.Fn acosh 72function appeared in 73.Bx 4.3 . 74