From Prof. Kahan at UC at Berkeley
.\" Copyright (c) 1985 Regents of the University of California.
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.\"	@(#)erf.3	6.2 (Berkeley) %G%
.\"
.TH ERF 3M  ""
.UC 6
.SH NAME
erf, erfc \- error functions
.SH SYNOPSIS
.nf
.B #include <math.h>
.PP
.B double erf(x)
.B double x;
.PP
.B double erfc(x)
.B double x;
.fi
.SH DESCRIPTION
Erf\|(x) returns the error function of x; where
.if n \{\
.PP
erf(x) = 2/sqrt(pi)\(**\|integral from 0 to x of exp(\-t\(**t) dt. \}
.if t \{\
erf\|(x) := 
(2/\(sr\(*p)\|\(is\d\s8\z0\s10\u\u\s8x\s10\d\|exp(\-t\u\s82\s10\d)\|dt. \}
.PP
Erfc\|(x) returns 1.0\-erf\|(x).
.PP
The entry for erfc is provided because of the extreme loss
of relative accuracy if erf\|(x) is called for large x
and the result subtracted from 1.
(e.g. for x = 10, 12 places are lost).
.SH SEE ALSO
math(3M)