       Re: How to obtain numberical value from an

• To: mathgroup at smc.vnet.net
• Subject: [mg80997] Re: How to obtain numberical value from an
• From: rob <josh2499 at hotmail.com>
• Date: Fri, 7 Sep 2007 02:09:07 -0400 (EDT)
• References: <fbohh3\$f5a\$1@smc.vnet.net>

```This looks interesting but what is it useful for? It appears
one must already know the form of the inversefunction to
apply it.  I feel sure I'm missing something; can someone
point me to an actual practical use of this inversefunction
concept? Thanks.

Bob Hanlon wrote:

> f[x_] := x;
>
> f /: InverseFunction[f] = f;
>
> InverseFunction[f][f[x]]
>
> x
>
> f[InverseFunction[f][x]]
>
> x
>
> InverseFunction[f][0.5]
>
> 0.5
>
> f[x_] := x^2;
>
> f /: InverseFunction[f] = Sqrt;
>
> InverseFunction[f][f[x]]
>
> Sqrt[x^2]
>
> f[InverseFunction[f][x]]
>
> x
>
> InverseFunction[f]
>
> 2
>
>
> Bob Hanlon
>
> ---- Nasser Abbasi <nma at 12000.org> wrote:
>
>>Hello;
>>
>>Are inverse function in Mathematica only have symbolic form and can't be
>>used to evaluate numerically?
>>
>>Anything I am trying is not working, this is a very simple example:
>>
>>f[x_] := x
>>InverseFunction[f][x]
>>
>>Now, how to evaluate anything out of the above? say for x=0.5, I expected to
>>get .5, but all I get is just
>>f(^-1)[x][.5]
>>
>>any ideas? Very little help on InverseFunctions.
>>
>>Nasser
>>
>>
>
>
>

```

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