1.\" Copyright (c) 1991 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.\" 4. 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.\" from: @(#)acosh.3 5.2 (Berkeley) 5/6/91 29.\" $FreeBSD$ 30.\" 31.Dd January 14, 2005 32.Dt ACOSH 3 33.Os 34.Sh NAME 35.Nm acosh , 36.Nm acoshf 37.Nd inverse hyperbolic cosine functions 38.Sh LIBRARY 39.Lb libm 40.Sh SYNOPSIS 41.In math.h 42.Ft double 43.Fn acosh "double x" 44.Ft float 45.Fn acoshf "float x" 46.Sh DESCRIPTION 47The 48.Fn acosh 49and the 50.Fn acoshf 51functions compute the inverse hyperbolic cosine 52of the real 53argument 54.Ar x . 55For a discussion of error due to roundoff, see 56.Xr math 3 . 57.Sh RETURN VALUES 58The 59.Fn acosh 60and the 61.Fn acoshf 62functions 63return the inverse hyperbolic cosine of 64.Ar x . 65If the argument is less than 1, 66.Fn acosh 67raises an invalid exception and returns an \*(Na. 68.Sh SEE ALSO 69.Xr asinh 3 , 70.Xr atanh 3 , 71.Xr exp 3 , 72.Xr fenv 3 , 73.Xr math 3 74.Sh HISTORY 75The 76.Fn acosh 77function appeared in 78.Bx 4.3 . 79