Services & Resources / Wolfram Forums / MathGroup Archive
-----

MathGroup Archive 2007

[Date Index] [Thread Index] [Author Index]

Search the Archive

A problem with FindRoot

  • To: mathgroup at smc.vnet.net
  • Subject: [mg83728] A problem with FindRoot
  • From: Vassilis Dimitrakas <vdimitrakas at googlemail.com>
  • Date: Thu, 29 Nov 2007 06:24:03 -0500 (EST)

Hi All,

I'd like some help with respect to a problem I have with the FindRoot, 
NSolve and FindInstance functions.
My version of Mathematica is 5.2

I define the function f as follows:

f[x_]:={
y/.FindRoot[y^3+1==x,{y,x}][[1]]
}[[1]]

f[x] returns the root of the equation y^3 + 1 == x, i.e. the value 
(x-1)^(1/3). f[x] has obviously a
unique root at x=1.

If I now try to find f[x]'s root with FindRoot, for example like

FindRoot[f[x]==0,{x,3}]

Mathematica (v 5.2) returns error messages and no solution. The same 
happens if I use instead NSolve
or FindInstance. Can you guys explain why this happens and suggest a 
remedy?

Thanks,

Vassilis



  • Prev by Date: Re: Convert nxn matrix to a column vector with (n^2) elements
  • Next by Date: Re: Rationalize
  • Previous by thread: Unable to access v6 internal data sources (paclets)
  • Next by thread: Re: A problem with FindRoot