Re: Integration variables

*To*: mathgroup at smc.vnet.net*Subject*: [mg78361] Re: [mg78307] Integration variables*From*: "matteo manni" <m_manni_m at hotmail.com>*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 answer. In the same post they suggested me to change d Cos[Ttheta] into -sin[Ttheta]dTtheta 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 cos[Ttheta]) ) to [0,Pi] (which is the equivalent for the Thata angle). >From: DrMajorBob <drmajorbob at bigfoot.com> >Reply-To: drmajorbob at bigfoot.com >To: mattew <m_manni_m at hotmail.com>, mathgroup at smc.vnet.net >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, >but... > >Rather than Integrate[f[x], g[x]], you must use Integrate[f[x] g'[x], x]. > >Bobby > >On Thu, 28 Jun 2007 03:20:02 -0500, mattew <m_manni_m at hotmail.com> 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 bigfoot.com _________________________________________________________________ Calcio, Quiz, Sudoku, Scacchi? Inizia la sfida su Messenger, GRATIS! http://www.messenger.it/giochi_e_attivita.html