Re: Log Equation
- To: mathgroup at smc.vnet.net
- Subject: [mg44800] Re: Log Equation
- From: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>
- Date: Thu, 27 Nov 2003 11:38:24 -0500 (EST)
- Organization: Universitaet Leipzig
- References: <bpuqjf$o65$1@smc.vnet.net>
- Reply-to: kuska at informatik.uni-leipzig.de
- Sender: owner-wri-mathgroup at wolfram.com
Hi, Mathematica *can* solve the equations in terms of the PolyLog[] function http://functions.wolfram.com/ZetaFunctionsandPolylogarithms/PolyLog/ and if someone use Mathematica he don't need a numerical method for it. Regards Jens Florian Jaccard wrote: > > Yes, the équation you want to solve is transcendental, so the only ways to > solve it are numerical. > > The most simple way is to use FindRoot. > But first, don't forget to draw f(x)=(1-x)/Log(x)-y ! You have to see an > approximation of the root you are searching ! > > For example, let y = -2 : > > In[1]:= Plot[(1 - x)/Log[x] + 2, {x, 0, 10},PlotRange -> {-4, 4}]; > > In[2]:= FindRoot[(1 - x)/Log[x] == -2, {x, 2}] > > Meilleures salutations > > Florian Jaccard > > -----Message d'origine----- > De : Bernard Bourée [mailto:bernard at bouree.net] > Envoyé : lun., 24. novembre 2003 06:05 > À : mathgroup at smc.vnet.net > Objet : Log Equation > > I 'm trying to find a way to solve the equation > > y = (1-x)/ Log(x) > > How can I find x when y is known ? > > Is there a numerical method ? > with series development? > > -- > Bernard Bourée > bernard at bouree.net