Re: Erf[InverseErf] -- making a function and its inverse cancel

• To: mathgroup at smc.vnet.net
• Subject: [mg69023] Re: Erf[InverseErf] -- making a function and its inverse cancel
• From: "MKT" <mktippett at gmail.com>
• Date: Sun, 27 Aug 2006 01:23:43 -0400 (EDT)
• References: <ecoq4t\$35n\$1@smc.vnet.net><ecp1hs\$803\$1@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

```Jean-Marc Gulliet wrote:
> mktippett at gmail.com wrote:
> > How can I get an expression like Erf[InverseErf[0,1/3]] to simplify to
> > 1/3?
> >
> > Cos[ArcCos[1/3]] gives 1/3. Is there some assumption that I'm missing?
> >
> > thanks,
> > Mike
> >
>
> For reason of efficiency, Mathematica does not call systematically the
> simplification rules. You must nudge Mathematica to force the
> simplification.
>
> In[1]:=
> FullSimplify[Erf[InverseErf[0, 1/3]]]
>
> Out[1]=
> 1
> -
> 3
>
> In[2]:=
> N[Erf[InverseErf[0, 1/3]]]
>
> Out[2]=
> 0.333333
>
> HTH,
> Jean-Marc

Thanks! I guess I need a newer version of mathematica :-). In version
4.1

Mathematica 4.1 for Linux
-- Motif graphics initialized --

In[1]:= FullSimplify[Erf[InverseErf[0, 1/3]]]

1
Out[1]= Erf[InverseErf[0, -]]
3

```

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