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: @(#)erf.3 6.4 (Berkeley) 4/20/91 33.\" $Id: erf.3,v 1.3 1993/08/14 13:42:38 mycroft Exp $ 34.\" 35.Dd April 20, 1991 36.Dt ERF 3 37.Os BSD 4.3 38.Sh NAME 39.Nm erf , 40.Nm erfc 41.Nd error function operators 42.Sh SYNOPSIS 43.Fd #include <math.h> 44.Ft double 45.Fn erf "double x" 46.Ft double 47.Fn erfc "double x" 48.Sh DESCRIPTION 49These functions calculate the error function of 50.Fa x . 51.Pp 52The 53.Fn erf 54calculates the error function of x; where 55.Bd -filled -offset indent 56.if n \{\ 57erf(x) = 2/sqrt(pi)\(**\|integral from 0 to x of exp(\-t\(**t) dt. \} 58.if t \{\ 59erf\|(x) := 60(2/\(sr\(*p)\|\(is\d\s8\z0\s10\u\u\s8x\s10\d\|exp(\-t\u\s82\s10\d)\|dt. \} 61.Ed 62.Pp 63The 64.Fn erfc 65function calculates the complementary error function of 66.Fa x ; 67that is 68.Fn erfc 69subtracts the result of the error function 70.Fn erf x 71from 1.0. 72This is useful, since for large 73.Fa x 74places disappear. 75.Sh SEE ALSO 76.Xr math 3 77.Sh HISTORY 78The 79.Fn erf 80and 81.Fn erfc 82functions appeared in 83.Bx 4.3 . 84