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MathGroup Archive 2002

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Re: Very urgent problem...PLEASE help me!

  • To: mathgroup at smc.vnet.net
  • Subject: [mg32863] Re: Very urgent problem...PLEASE help me!
  • From: Erk Jensen <Erk.Jensen at cern.ch>
  • Date: Sat, 16 Feb 2002 04:35:20 -0500 (EST)
  • Organization: CERN http://www.cern.ch
  • References: <a4iftr$9q4$1@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

Detlef Mueller wrote:
> 
> Hi out there!
> 
> I'm a student working on a test with Mathematica...and I've got
> massive problems with this task here:
> 
> http://home.t-online.de/home/harrytasker/Task.nb
> 
> If it's not working, here's a scan of it
> 
> http://home.t-online.de/home/harrytasker/scan6.JPG
> 
> (Sorry it's in german..anyhow, it is obviously a system of equations.
> I just have to plot the solution of y3(t) in the limits of 0<=w t<=4
> Pi).
> 
> But how do I do it?
> It shouldn't be that much work...but I don't get the idea HOW.
> I tried with LinearSolve...but out comes a (very complicated) result,
> which I'm not able to plot somehow.
> Also, there's this Y0-thing..nothing is specified about this, should I
> just take it as a constant (because Plot requests a numerical value!).
> 
> So, you see, I'm rather confused...please help me!
> 
> THANKS A LOT IN ADVANCE!
> 
> Bye
> Detlef Mueller
> 
> P.S.:I'm using Mathematica 3.0 on PC...if it's important.

You have known_vector = matrix dot unknown_vector. ( ...well, I guess Y0(x) is
BesselY[0,x] ...)

So you have to do Inverse[matrix] dot known_vector to get the unknown_vector,
the 3rd component of which is your solution. You replace w t by another
variable, and plot. Since you want it logarithmic, you have to think about what
to do with negative numbers ...

All this has nothing to do with Mathematica, btw.

Ciao
   -erk-


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