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MathGroup Archive 2004

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Re: how can I solve a function Erfc

  • To: mathgroup at smc.vnet.net
  • Subject: [mg48494] Re: how can I solve a function Erfc
  • From: "Peter Pein" <petsie at arcor.de>
  • Date: Wed, 2 Jun 2004 04:22:00 -0400 (EDT)
  • References: <c99d7f$k3b$1@smc.vnet.net> <c9ccj1$5sn$1@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

"David W. Cantrell" <DWCantrell at sigmaxi.org> schrieb im Newsbeitrag
news:c9ccj1$5sn$1 at smc.vnet.net...
> "Florian Jaccard" <florian.jaccard at eiaj.ch> wrote:
> [snip]
> > In[9]:= L/(4*(Dg*t)^(1/2)) == InverseErfc[0.9]
> >
> > In[10]:= Solve[{%, Dg == 5*10^5}, t]
>
> My question now is: Since [2] (using 0.9) works,
> why does [1] (using 9/10 instead) fail?
>
>
> In[1]:= Solve[L/(4*(Dg*t)^(1/2)) == InverseErfc[9/10], t]
>
> Out[1]= {}
>
> In[2]:= Solve[L/(4*(Dg*t)^(1/2)) == InverseErfc[0.9], t]
>
> Out[2]= {{t -> (7.916014709627096*L^2)/Dg}}
>
>
> Surely [1] indicates a bug of some sort.
>
> David Cantrell


In[1]:=
Solve[L/(4*(Dg*t)^(1/2)) ==
   InverseErfc[9/10], t]
Out[1]=
{{t -> L^2/(16*Dg*InverseErf[
        Infinity, -(9/10)]^2)}}
??
-- 
Peter Pein, Berlin
to write to me, start the subject with [



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