       Re: 1 equals 3 (among others)

• To: mathgroup at smc.vnet.net
• Subject: [mg32200] Re: 1 equals 3 (among others)
• From: Stegemann at physikDONOT.SPAMtu-berlin.de (Grischa Stegemann)
• Date: Sat, 5 Jan 2002 00:10:43 -0500 (EST)
• References: <a13v7l\$dgb\$1@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

```On Fri, 4 Jan 2002 10:13:09 +0000 (UTC), Grischa Stegemann wrote:
>
> In:=f[x_] = (4 - x + Sqrt[-4*(3 - x) + (x - 4)^2])/2;
> In:=Simplify[-4*(3 - x) + (x - 4)^2]
> Out=(-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 --

```

• Prev by Date: Re: 1 equals 3 (among others)
• Next by Date: Re: 1 equals 3 (among others)
• Previous by thread: Re: 1 equals 3 (among others)
• Next by thread: Re: 1 equals 3 (among others)