erf.3m

<B>Digital的Unix操作系统VAX 4.2源码</B>

.\" SCCSID: @(#)erf.3m	8.2	3/28/91
'\" e
.TH erf 3m VAX
.SH Name
erf, erfc \- error function and complementary error function
.SH Syntax
.B #include <math.h>
.PP
.B double erf (x)
.br
.B double x;
.PP
.B double erfc (x)
.br
.B double x;
.SH Description
.if t .ig
.PP
NOTE: Your terminal may not be able to accurately display 
the special math symbols in this reference page. See the 
.I ULTRIX Programmer's Manual, Unsupported
for a complete description of the math symbols. 
..
.NXR "erf subroutine"
.NXR "erfc subroutine" 
.NXR "error function"
.PP
The
.PN erf
function 
returns the error function of
.IR x ,
defined as
.EQ
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.EN
.PP
The
.PN erfc
function,
which returns 1.0 \-
.IR erf(x) ,
is provided because of the
extreme loss of relative accuracy if
.I erf(x)
is called for large
.I x
and the result subtracted
from 1.0 (e.g. for
.I x
= 5, 12 places are lost).
.SH See Also
exp(3m)
.br
.I ULTRIX Programmer's Manual, Unsupported