1.\" Copyright (c) 1985, 1991, 1993 2.\" The Regents of the University of California. All rights reserved. 3.\" 4.\" %sccs.include.redist.roff% 5.\" 6.\" @(#)erf.3 8.1 (Berkeley) 06/04/93 7.\" 8.Dd 9.Dt ERF 3 10.Os BSD 4.3 11.Sh NAME 12.Nm erf , 13.Nm erfc 14.Nd error function operators 15.Sh SYNOPSIS 16.Fd #include <math.h> 17.Ft double 18.Fn erf "double x" 19.Ft double 20.Fn erfc "double x" 21.Sh DESCRIPTION 22These functions calculate the error function of 23.Fa x . 24.Pp 25The 26.Fn erf 27calculates the error function of x; where 28.Bd -filled -offset indent 29.if n \{\ 30erf(x) = 2/sqrt(pi)\(**\|integral from 0 to x of exp(\-t\(**t) dt. \} 31.if t \{\ 32erf\|(x) := 33(2/\(sr\(*p)\|\(is\d\s8\z0\s10\u\u\s8x\s10\d\|exp(\-t\u\s82\s10\d)\|dt. \} 34.Ed 35.Pp 36The 37.Fn erfc 38function calculates the complementary error function of 39.Fa x ; 40that is 41.Fn erfc 42subtracts the result of the error function 43.Fn erf x 44from 1.0. 45This is useful, since for large 46.Fa x 47places disappear. 48.Sh SEE ALSO 49.Xr math 3 50.Sh HISTORY 51The 52.Fn erf 53and 54.Fn erfc 55functions appeared in 56.Bx 4.3 . 57