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.

--- 16 unchanged lines hidden (view full) ---

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 .