Re: Possible Mathematica 4.0 bug

• To: mathgroup at smc.vnet.net
• Subject: [mg30836] Re: Possible Mathematica 4.0 bug
• From: Ioan Alexandre Romoscanu <romoscanu at imes.mavt.ethz.ch>
• Date: Thu, 20 Sep 2001 03:51:30 -0400 (EDT)
• Organization: Swiss Federal Institute of Technology (ETHZ)
• References: <9o97d9\$cg2\$1@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

```I have seen lots of these things.

1. is not equal to 1 according to mathematica.
Check the attached picture to see an explicit example.
[Contact the author to get this - moderator/

Cheers

I.

Christian Mikkelsen wrote:

> The following problem cost most of a mornings work and
> I ended up attributing it to a bug but before I send
> it off to Wolfram Research I'd like some comments.
>
> I have a polynomial defined as
>
> H[z_]= (1/z^6)
> ((0.17897972007618376+0.1832666067995157
> I)((0.07806788263644916+0.9898486037537829 I)+I
> z)((-1.0304811754750547-1.1012670896195078
> I)+z)((-0.4716966687204682-0.6843778680006037
> I)+z)((-0.4537703518350889+0.7354674436955
> I)+z)((-0.32047121654063226+0.18872779388498095
> I)+z)((0.7411819790476893+0.15538114678579676 I)+z));
>
> with some auxiliary definitions
>
> f[w_] = Arg[H[Exp[I w]]];
> fmm[w_] = (f[w+h]-2f[w]+f[w-h])/h^2 /.h->10^(-6) //
> Simplify;
> d = 1 10^8;
>
> The following results in an erroneous(?)
> simplification
>
> disp[l_]=fmm[d/l] //Simplify
>
> but defining d = 1.0 10^8 gives the correct(?) result.
> A different result at any rate. Ok, so in principle I
> have a workaround but I would be happy to know if the
> issue also exists in version 4.1. I don't currently
>
> Finally, it is of course possible that I have missed
> something so I would be most happy to get feedback on
> that as well.
>
> Cheers,
>
> Christian Mikkelsen
>
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