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MathGroup Archive 2005

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Re: RSolve and complex solutions

  • To: mathgroup at smc.vnet.net
  • Subject: [mg54719] Re: RSolve and complex solutions
  • From: "Jens-Peer Kuska" <kuska at informatik.uni-leipzig.de>
  • Date: Mon, 28 Feb 2005 03:27:04 -0500 (EST)
  • Organization: Uni Leipzig
  • References: <cvrq1t$p28$1@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

Hi,

a) RSolve work pure symbolical, there can't be rounding errors
b) RSolve[] will Solve[] at least a system of equations and
   this can produce complex solutions even for real input.

Regards
  Jens

"Skirmantas" <skirmantas.janusonis at yale.edu> schrieb im Newsbeitrag 
news:cvrq1t$p28$1 at smc.vnet.net...
> It may be a basic math question, but it would be helpful if somebody
> could briefly comment on it. If I have a system of recursion equations
> with real coefficients and solve it numerically step-by-step, all my
> solutions at all time steps are (obviously) real. If, however, I use
> RSolve to get the general formulas for these solutions, some of them
> become complex numbers. My understanding is the imaginary parts of
> these numbers are due to rounding errors and the actual solutions are
> only the real parts. Am I right?
> 



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