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MathGroup Archive 2002

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Re: 1 equals 3 (among others)

  • To: mathgroup at smc.vnet.net
  • Subject: [mg32214] Re: 1 equals 3 (among others)
  • From: "James Richitt" <james at citicom.com>
  • Date: Sun, 6 Jan 2002 03:38:30 -0500 (EST)
  • References: <a13v7l$dgb$1@smc.vnet.net> <a162s3$pne$1@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

If you have problems seeing the full numerical values along the y-axis, you
should try the PlotRegion switch...

Plot[ f[x], {x, 0, 5}, PlotRegion->{{0.1, 1}, {0.1, 1}}]

James


"Grischa Stegemann" <Stegemann at physikDONOT.SPAMtu-berlin.de> wrote in
message news:a162s3$pne$1 at smc.vnet.net...
> On Fri, 4 Jan 2002 10:13:09 +0000 (UTC), Grischa Stegemann wrote:
> >
> > In[1]:=f[x_] = (4 - x + Sqrt[-4*(3 - x) + (x - 4)^2])/2;
> > In[2]:=Simplify[-4*(3 - x) + (x - 4)^2]
> > Out[2]=(-2 + x)^2
>
> Oh stupid fool I am! All the time I have dealt with complex numbers
> but only in this special case everything becomes real. So I have
> totally ignored that Sqrt[x^2]=Abs[x]. This of course explains the
> numbers I mentioned.
>
> Nevertheless I found out that this wasn't actually my problem. The
> actual problem arised from the plot
> Plot[f[x],{x,0,5}]
> because I have neglected the numbers at the y-axis and thought that
> Mathematica is giving me lots of rubbish.
> In this plot you can see numerical noise which can be hidden by
> e.g. giving PlotRange->{0,3}) but which doesn't appear if you plot
> g[x_]=Sqrt[-4*(3 - x) + (x - 4)^2];
> Plot[g[x],{x,0,5}].
>
> OK, this is not really essential... ;-)
>
>
> Thanks to all who pointed me to my stupidity.
>
>
> Bye, Grischa
> --
> -------------------------------------------------------------------------
>    Grischa Stegemann                     Technische Universität Berlin --
>
>




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