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MathGroup Archive 2007

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Re: Re: How to obtain numberical value from an

  • To: mathgroup at smc.vnet.net
  • Subject: [mg81029] Re: [mg80997] Re: How to obtain numberical value from an
  • From: DrMajorBob <drmajorbob at bigfoot.com>
  • Date: Sat, 8 Sep 2007 03:54:42 -0400 (EDT)
  • References: <fbohh3$f5a$1@smc.vnet.net> <19345541.1189157227539.JavaMail.root@m35>
  • Reply-to: drmajorbob at bigfoot.com

Mathematica uses inverse functions to Solve equations, for instance.

Bobby

On Fri, 07 Sep 2007 01:09:07 -0500, rob <josh2499 at hotmail.com> wrote:

> 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][4]
>>
>> 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
>>>
>>>
>>
>>
>>
>
>



-- =

DrMajorBob at bigfoot.com


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