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MathGroup Archive 2007

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Re: Integration variables

  • To: mathgroup at
  • Subject: [mg78351] Re: Integration variables
  • From: dh <dh at>
  • Date: Thu, 28 Jun 2007 06:37:11 -0400 (EDT)
  • References: <f5vr6e$j12$>

Hi mattew,

obviously Cos[Theta] is not a variable but a function. If you want to 

use it as a varible you must give it a valid name,e.g. costheta. But 

then you must write the integrand as a function of your variable, e.g.:


hope this helps, Daniel

mattew 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.


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