Re: Integration variables
- To: mathgroup at smc.vnet.net
- Subject: [mg78351] Re: Integration variables
- From: dh <dh at metrohm.ch>
- Date: Thu, 28 Jun 2007 06:37:11 -0400 (EDT)
- References: <f5vr6e$j12$1@smc.vnet.net>
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.:
Integrate[ArcCos[costheta],{costheta,-1,1}]
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.
>