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Re: RowReduce::luc when using NSolve

  • To: mathgroup at smc.vnet.net
  • Subject: [mg99189] Re: RowReduce::luc when using NSolve
  • From: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>
  • Date: Wed, 29 Apr 2009 06:38:34 -0400 (EDT)
  • Organization: Uni Leipzig
  • References: <gt6fkm$rru$1@smc.vnet.net>
  • Reply-to: kuska at informatik.uni-leipzig.de

Hi,

NSolve[{BesselJ[0, 20] - BesselJ[0, 20] r[0] ==
    3 I BesselJ[0, 60 I] t[0],
   BesselJ[0, 20] + BesselJ[0, 20] r[0] == BesselJ[0, 60 I] t[0]}, {r[
    0], t[0]}, WorkingPrecision -> 30]

?

Regards
   Jens

mereandor wrote:
> I try to solve a linear equation with the following input to mathematica:
> 
> NSolve[{BesselJ[0, 20] - BesselJ[0, 20] r[0] == 3 I BesselJ[0, 60 I] t[0], BesselJ[0, 20] + BesselJ[0, 20] r[0] == BesselJ[0, 60 I] t[0]}, {r[0], t[0]}]
> 
> but I get
> 
> RowReduce::luc: Result for RowReduce of badly conditioned matrix \
> {{-0.167025+0. I,-1.61061*10^9-<<21>> I,0.167025+0. I},{<<1>>}} may \
> contain significant numerical errors. >>
> 
> This is only the simplest instance of my problem (2(n+1) equations in equally numbered variables). If I don't write the equations down literally but insert them into NSolve as a Table[] statement I don't even get the warning. Then the equations are solved only partially expressing t[n] as linear combination of r[n].
> 
> I use Mathematica 6.0
> 
> How can I resolve this?
> 
> Thanks in advance for any help!
> 


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