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Re: Viewing real solution out of Root[#] output

  • To: mathgroup at smc.vnet.net
  • Subject: [mg50658] Re: Viewing real solution out of Root[#] output
  • From: Paul Abbott <paul at physics.uwa.edu.au>
  • Date: Wed, 15 Sep 2004 07:54:30 -0400 (EDT)
  • Organization: The University of Western Australia
  • References: <ci8mmt$bsj$1@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

In article <ci8mmt$bsj$1 at smc.vnet.net>, mbekkali at gmail.com (Mukhtar) 
wrote:

> Is there a way to view the real solution (no matter how many pages it
> would take just to print it) for output of the form something like
> Root[x#1+2x#1-3#2] and so on, where x is some symbolic parameter?

As an example,

  ToRadicals[Root[#^3 - #^2 + 1 & , 1]]

Note that some expressions cannot be expressed as radicals. For example,

  Root[#^5 - # + 1 & , 1]

Section 3.4.3 of the Mathematica book states that:

  However, you should realize that there are some special cases in which 
  a reduction to radicals is in principle possible, but Mathematica 
  cannot find it. The simplest example is the equation 

    x^5 + 20 x + 32 == 0

And I must still ask, why do you want to view the real solution, 
especially if it takes many pages to print out, and what do you want to 
do with it?

Cheers,
Paul

-- 
Paul Abbott                                   Phone: +61 8 9380 2734
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