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Re: How to obtain numberical value from an

• To: mathgroup at smc.vnet.net
• Subject: [mg80944] Re: [mg80916] How to obtain numberical value from an
• From: Bob Hanlon <hanlonr at cox.net>
• Date: Thu, 6 Sep 2007 05:22:50 -0400 (EDT)
• Reply-to: hanlonr at cox.net

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
> 
>