<A NAME=ERF>
<TITLE>ERF</TITLE></A>
<b><a href=r37_idx.html>INDEX</a></b><p><p>
<B>ERF</B> _ _ _ _ _ _ _ _ _ _ _ _ <B>operator</B><P>
<P>
<P>
<P>
The <em>erf</em> operator represents the error function, defined by
<P>
<P>
erf(x) = (2/sqrt(pi))*int(e^(-x^2),x)
<P>
<P>
A limited number of its properties are known to the system, including the
fact that it is an odd function. Its derivative is known, and from this,
some integrals may be computed. However, a complete integration procedure
for this operator is not currently included.
<P>
<P>
<P> <H3>
examples: </H3>
<P><PRE><TT>
erf(0);
0
erf(-a);
- ERF(A)
df(erf(x**2),x);
4*SQRT(PI)*X
------------
4
X
E *PI
int(erf(x),x);
2
X
E *ERF(X)*PI*X + SQRT(PI)
---------------------------
2
X
E *PI
</TT></PRE><P>