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MathGroup Archive 2005

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Re: Simplify further

  • To: mathgroup at smc.vnet.net
  • Subject: [mg61809] Re: [mg61791] Simplify further
  • From: Bob Hanlon <hanlonr at cox.net>
  • Date: Mon, 31 Oct 2005 01:17:04 -0500 (EST)
  • Reply-to: hanlonr at cox.net
  • Sender: owner-wri-mathgroup at wolfram.com

FullSimplify eliminates the Sqrt

$Version

5.2 for Mac OS X (June 20, 2005)

f[x_] := c/(x - p) + Conjugate[c]/(x - Conjugate[p])

soln=Simplify[Solve[D[f[x],x]==0,x]];

FullSimplify[f[x]/.soln]

{(Re[c]^2*Sign[c])/(Im[c]*Im[p]*Sign[c] - 
    c*Im[p]*Sign[Im[p]]), 
  Re[c]^2/(Im[p]*(Im[c] + Conjugate[c]*Sign[c]*
      Sign[Im[p]]))}


Bob Hanlon

> 
> From: "Thomas Schmelzer" <thomas.??? at balliol.ox.ac.uk>
To: mathgroup at smc.vnet.net
> Date: 2005/10/30 Sun AM 12:43:20 EDT
> Subject: [mg61809] [mg61791] Simplify further
> 
> Hi experts,
> 
> Let
> 
> f[x_] := c/(x - p) + c\[Conjugate]/(x - p\[Conjugate])
> 
> I am interested in local extrema
> 
> Solve[D[f[x], x] == 0, x]
> 
> Mathematica gives me a list.
> 
> I plug those values into f again.
> 
> Using the Simplify command I get expression as
> 
> sqrt(- c conjugate c ( p - conjugate p ) ^2 )
> 
> Is there a way that Mathematica simplifies that to
> 
> 4*(abs (c))^2  (Im p)^2
> 
> cheers
> 
> Thomas
> 
> 
> 
> 
> 


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