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MathGroup Archive 2006

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Re: sorting list of roots af a transcendental function

  • To: mathgroup at smc.vnet.net
  • Subject: [mg65273] Re: sorting list of roots af a transcendental function
  • From: Bill Rowe <readnewsciv at earthlink.net>
  • Date: Thu, 23 Mar 2006 06:58:34 -0500 (EST)
  • Sender: owner-wri-mathgroup at wolfram.com

On 3/22/06 at 6:13 AM, dule23 at gmx.de (Dule) wrote:

>for calculating a model i need values for x which are given by the
>transcendental function Cot[x] == x/a - a/(4*x). a is a parameter
>0<a<200. i obtained the roots with Table and FindRoot:
>Table[FindRoot[Cot[x] == x/a - a/(4*x), {x, i}], {i, 1, 50}]]

>I have two questions: 
>1. Is there a better way to do this?

Table seems fine. Another way would be

FindRoot[Cot[x] == x/a -a/(4 x), {x, #}]&/@Range[50]

>2. How can i construct a list, where the values for x, which appear
>multiple are dropped?

Use Union, i.e.

Union[FindRoot[Cot[x] == x/a -a/(4 x), {x, #}]&/@Range[50]]
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