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Re: Strange "not a symbol or valid symbol name" error


Flip wrote:
> Greetings all, I'm using Mathematica 5.0 and have been getting a
> strange error message:
> 
> Unique::usym :
> 10000000000 is not a symbol or a valid symbol name
> 
> This comes from the following integral:
> 
> Integrate[E^(-x) Sqrt[x^2-9], {x,3,5}]
> 
> The limits of integration don't matter much so long as they keep the
> integrand real.
> 
> I don't understand this and am not quite sure how to fix the problem.
> (It's a well defined definite integral, right? It's real in the domain
> of integration and nondivergent.)
> 
> Thanks,
> Flip
> 
First, clear the definition of any variables or quit the kernel, then 
use *NIntegrate* since *Integrate* will not return any symbolic value 
but the integrand itself.

In[1]:=
Clear["Global`*"];
Integrate[Sqrt[x^2 - 9]/E^x, {x, 3, 5}]

Out[2]=
Integrate[Sqrt[-9 + x^2]/E^x, {x, 3, 5}]

In[3]:=
NIntegrate[Sqrt[x^2 - 9]/E^x, {x, 3, 5}]

Out[3]=
0.08562828535776716

In[4]:=
$Version

Out[4]=
"5.2 for Microsoft Windows (June 20, 2005)"

Regards,
/J.M.


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