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MathGroup Archive 2004

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Re: Q: Solve gives complex solution where there is a noncomplex solution how to get the last one?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg50329] Re: [mg50300] Q: Solve gives complex solution where there is a noncomplex solution how to get the last one?
  • From: DrBob <drbob at bigfoot.com>
  • Date: Fri, 27 Aug 2004 02:57:51 -0400 (EDT)
  • References: <200408261050.GAA16310@smc.vnet.net>
  • Reply-to: drbob at bigfoot.com
  • Sender: owner-wri-mathgroup at wolfram.com

Solve[x*(y/(1 + y^2)^(1/2)) == a, y]

{{y -> -(a/Sqrt[-a^2 + x^2])},
   {y -> a/Sqrt[-a^2 + x^2]}}

Bobby

On Thu, 26 Aug 2004 06:50:41 -0400 (EDT), Dick Barends <dick.barends at wxs.nl> wrote:

> Hello,
>
> The following line
>
> Solve[x y / ( 1 + y^2 )^0.5 == a, y]
>
> Gives a complex solution : (0.+ i )a / (a^2 - x^2)^0.5
> Which is correct but could be simpler, not complex
>
> The solution I expected is: a/(x^2 - a^2)^0.5
>
> How can I instruct Mathematica (Solve) to give the simple solution directly.
>
> kind regards
> Dick Barends
>
>
>
>



-- 
DrBob at bigfoot.com
www.eclecticdreams.net


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