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

*To*: mathgroup at smc.vnet.net*Subject*: [mg60218] Re: Strange "not a symbol or valid symbol name" error*From*: Jean-Marc Gulliet <jeanmarc.gulliet at gmail.com>*Date*: Thu, 8 Sep 2005 04:52:56 -0400 (EDT)*Organization*: The Open University, Milton Keynes, U.K.*References*: <dfm86d$hek$1@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

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.