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.\" $FreeBSD$ 34.\" 35.Dd April 20, 1991 36.Dt ERF 3 37.Os 38.Sh NAME 39.Nm erf , 40.Nm erff , 41.Nm erfc , 42.Nm erfcf 43.Nd error function operators 44.Sh LIBRARY 45.Lb libm 46.Sh SYNOPSIS 47.In math.h 48.Ft double 49.Fn erf "double x" 50.Ft float 51.Fn erff "float x" 52.Ft double 53.Fn erfc "double x" 54.Ft float 55.Fn erfcf "float x" 56.Sh DESCRIPTION 57These functions calculate the error function of 58.Fa x . 59.Pp 60The 61.Fn erf 62and the 63.Fn erff 64functions calculate the error function of x; where 65.Bd -ragged -offset indent 66.if n \{\ 67erf(x) = 2/sqrt(pi)\(**\|integral from 0 to x of exp(\-t\(**t) dt. \} 68.if t \{\ 69erf\|(x) := 70(2/\(sr\(*p)\|\(is\d\s8\z0\s10\u\u\s8x\s10\d\|exp(\-t\u\s82\s10\d)\|dt. \} 71.Ed 72.Pp 73The 74.Fn erfc 75and the 76.Fn erfcf 77functions calculate the complementary error function of 78.Fa x ; 79that is 80.Fn erfc 81subtracts the result of the error function 82.Fn erf x 83from 1.0. 84This is useful, since for large 85.Fa x 86places disappear. 87.Sh SEE ALSO 88.Xr math 3 89.Sh HISTORY 90The 91.Fn erf 92and 93.Fn erfc 94functions appeared in 95.Bx 4.3 . 96