RE: I need some help about this error

*To*: mathgroup at smc.vnet.net*Subject*: [mg39308] RE: [mg39305] I need some help about this error*From*: "Wolf, Hartmut" <Hartmut.Wolf at t-systems.com>*Date*: Tue, 11 Feb 2003 04:40:44 -0500 (EST)*Sender*: owner-wri-mathgroup at wolfram.com

>-----Original Message----- >From: spin9 at terra.com.br [mailto:spin9 at terra.com.br] To: mathgroup at smc.vnet.net >Sent: Monday, February 10, 2003 7:08 AM >To: mathgroup at smc.vnet.net >Subject: [mg39308] [mg39305] I need some help about this error > > >f[x_] := x^2 - 2 >Ne[x_] := x - f[x]/f'[x] >ap = NestList[Ne, 1.5, 5] >tang[h_] := f[h] + f'[h](x - h) >t = tang /@ ap > >Plot[{t}, {x, -10, 10}, AxesOrigin -> {0, 0}, > PlotRange -> {{-5, 5}, {-3, 5}}] > >Now, How can I plot the last command? > >I got the following errors: > >Plot::"plnr": "\!\(te[x]\) is not a machine-size real number at >\!\(x\) = \ >\!\(-9.999999166666667`\)." >Plot::"plnr": "\!\(te[x]\) is not a machine-size real number at >\!\(x\) = \ >\!\(-9.188660168541684`\)." > >I want to make a "program" that will plot the successives tangent >lines of approximations of any function (when possible) using the >Newton Methods... any idea on how can I implement or solve that >problem? > >Thank you very much! > In[8]:= Attributes[Plot] Out[8]= {HoldAll, Protected} So you have to evaluate your arguments. But, I fear, you'll not see too much, as Newton convergences is to rapidly in this case; but here's the method: With[{delta = 10^-1, x0 = Sqrt[2]}, Plot[Evaluate[Prepend[t, f[x]]], Evaluate[Prepend[x0 + delta*{-1, 1}, x]], PlotStyle -> Prepend[Table[{}, {Length[t]}], {Hue[0], Thickness[.005]}], PlotRange -> {All, Thread[f[x0 + delta*{-1, 1}]]}]] You may play with delta, and pull large the graphics. -- Hartmut Wolf