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Re: Rearrange equation

  • To: mathgroup at smc.vnet.net
  • Subject: [mg111585] Re: Rearrange equation
  • From: Bill Rowe <readnews at sbcglobal.net>
  • Date: Fri, 6 Aug 2010 06:57:39 -0400 (EDT)

On 8/5/10 at 7:32 AM, tonja.krueger at web.de (Tonja Krueger) wrote:

>I want to rearrange the equation below so that it would look like:
>x-> .... I tried:
>Solve[G==-(Sqrt[\[Pi]/2]*Erfc[x]*(-\[Mu]+Log[x]))/(2*Sqrt[\[Pi]]*\[
>Sigma]),x] But then I got the error message: Solve::tdep: The
>equations appear to involve the variables to be  solved for in an
>essentially non-algebraic way. Is there a way to solve the equation?

There is no closed form symbolic solution for that equation. You
can find numeric solutions using FindRoot after given G, \[Mu]
and \[Sigma] numeric values. For example:

In[6]:= FindRoot[1 + Erfc[x] Log[x]/(2 Sqrt[2]), {x, .001, 10}]

Out[6]= {x->0.0499295}

Here, I've set G = \[Sigma] = 1 and \[Mu] = 0



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