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Re: Integration variables

  • To: mathgroup at
  • Subject: [mg78361] Re: [mg78307] Integration variables
  • From: "matteo manni" <m_manni_m at>
  • Date: Fri, 29 Jun 2007 05:43:37 -0400 (EDT)

I think that the problem was that I was triyn to integrate in cos[Ttheta], 
which is a funtion and not a variable, as it was underlined in the previous 
In the same post they suggested me to change

d Cos[Ttheta]



in order to have a valid integration variable. In this case I have to change 
the interval of integration from [-1,1] that I had before (referring to 
) to [0,Pi] (which is the equivalent for the Thata angle).

>From: DrMajorBob <drmajorbob at>
>Reply-To: drmajorbob at
>To: mattew <m_manni_m at>, mathgroup at
>Subject: Re: [mg78307] Integration variables
>Date: Thu, 28 Jun 2007 11:34:46 -0500
>You didn't post the code, so it's just a guess what you actually entered,  
>Rather than Integrate[f[x], g[x]], you must use Integrate[f[x] g'[x], x].
>On Thu, 28 Jun 2007 03:20:02 -0500, mattew <m_manni_m at> wrote:
>>Hi everybody, Mathematica gives us the possibility to use spherical  
>>coordinates (r,Ttheta,Pphi): I'm trying to write an integral in the  polar 
>>angle Ttheta of the form:
>>Integral in [-1,1] Ttheta dCos(Ttheta)
>>where Ttheta is the polar angle and the integration variable is the  
>>cosine of Ttheta in the interval [-1,1].
>>I got the following error:
>>ntegrate::ivar: "Cos[Ttheta] is not a valid variable."
>>Does anyone knows the reason for that?
>>p.s: It happens with any system of coordinates, actually.
>DrMajorBob at

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