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Re: Problems with Module

  • To: mathgroup at smc.vnet.net
  • Subject: [mg112069] Re: Problems with Module
  • From: Tomas Garza <tgarza10 at msn.com>
  • Date: Sat, 28 Aug 2010 07:03:43 -0400 (EDT)

I think you're using an invalid notation for your derivatives. The on-line help uses a straight ' to denote a derivative (q.v.). For the texts you had better use the writing assistant palette, special symbols, and you'll find a prime and a double prime symbol.
Making these changes, I get a clean result for t == 0, but as soon as the slider is moved an error is reported, which has to do with your code, I guess.

Saludos,

Tomas

> Date: Fri, 27 Aug 2010 04:07:29 -0400
> From: sterraza at uacj.mx
> Subject: [mg112052] Problems with Module
> To: mathgroup at smc.vnet.net
>
>  Hi!
>
>  The following is a slight modification of a code that works fine. But this
>  one does not work.
>  However, if I empty the list of local variables in Module, Then it works!
>  Could some of you enlighten me?
>
>  f[t_]:==4 Sin[t];g[t_]:==2 Cos[t];a==0;b==2\[Pi];
>  DerVectConst[f,g,a,b]
>
>  DerVectConst[f_,g_,a_,b_]:==Module[{r,vel,acel,unitario,derivadadeu,du},
>  $Assumptions==t\[Element]Reals;
>
>  r[t_]=={f[t],g[t]};
>  vel[t_]==(r^\[Prime])[t];
>  acel[t_]==(r^\[DoublePrime])[t];
>  unitario[t_]==acel[t]/Norm[acel[t]];
>  derivadadeu[t_]==(unitario^\[Prime])[t];
>  du[t_]==derivadadeu[t]//FullSimplify;
>
>  Manipulate[
>
>  f1==Graphics[{Thick,Blue,Arrow[{r[t],r[t]+du[t]}]}];
>  f2==Graphics[{Thick,Green,Arrow[{r[t],r[t]+unitario[t]}]}];
>  g1==ParametricPlot[r[t],{t,a,b},AspectRatio->Automatic,PlotStyle->{Thick, Red}];
>  txt==Graphics[{Text[Style["\!\(\*OverscriptBox[\"u\",
>  \"^\"]\)",18,Bold],(r[t]+1.1unitario[t])],Text[Style["\!\(\*OverscriptBox[\"u\",
>  \"^\"]\)^\[Prime]",18,Bold],(r[t]+1.1du[t])]}];
>  punto==Graphics[{PointSize[.02],Point[r[t]]}];
>  Show[g1,f1,f2,txt,punto,PlotRange->All]
>  ,{t,a,b}]
>  ]
>
 		 	   		 


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