1.\" Copyright (c) 1985, 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.\" 3. All advertising materials mentioning features or use of this software 13.\" must display the following acknowledgement: 14.\" This product includes software developed by the University of 15.\" California, Berkeley and its contributors. 16.\" 4. Neither the name of the University nor the names of its contributors 17.\" may be used to endorse or promote products derived from this software 18.\" without specific prior written permission. 19.\" 20.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 21.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 24.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30.\" SUCH DAMAGE. 31.\" 32.\" from: @(#)atanh.3 5.2 (Berkeley) 5/6/91 33.\" $FreeBSD: src/lib/msun/man/atanh.3,v 1.13 2005/01/28 21:14:16 ru Exp $ 34.\" 35.Dd January 14, 2005 36.Dt ATANH 3 37.Os 38.Sh NAME 39.Nm atanh , 40.Nm atanhf 41.Nd inverse hyperbolic tangent functions 42.Sh LIBRARY 43.Lb libm 44.Sh SYNOPSIS 45.In math.h 46.Ft double 47.Fn atanh "double x" 48.Ft float 49.Fn atanhf "float x" 50.Sh DESCRIPTION 51The 52.Fn atanh 53and the 54.Fn atanhf 55functions compute the inverse hyperbolic tangent 56of the real 57argument 58.Ar x . 59For a discussion of error due to roundoff, see 60.Xr math 3 . 61.Sh RETURN VALUES 62The 63.Fn atanh 64and the 65.Fn atanhf 66functions 67return the inverse hyperbolic tangent of 68.Ar x 69if successful. 70If the argument has absolute value 1, a divide-by-zero exception 71is raised and an infinity is returned. 72If 73.Ar |x| 74> 1, an invalid exception is raised and an \*(Na is returned. 75.Sh SEE ALSO 76.Xr acosh 3 , 77.Xr asinh 3 , 78.Xr exp 3 , 79.Xr fenv 3 , 80.Xr math 3 81.Sh HISTORY 82The 83.Fn atanh 84function appeared in 85.Bx 4.3 . 86