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//N bug, but WHY?

• To: mathgroup at smc.vnet.net
• Subject: [mg58634] //N bug, but WHY?
• From: "symbio" <symbio at has.com>
• Date: Mon, 11 Jul 2005 04:19:20 -0400 (EDT)
• Reply-to: "symbio" <symbio at sha.com>
• Sender: owner-wri-mathgroup at wolfram.com

Evaluating (using //N) two exact same expressions, gives wrong answer unless 
fullsimplify is used first, I spent 2 days on a problem thinking my answer 
was wrong, but turned out Mathematica 5 was giving me buggy answers, I 
debugged it to this point, but WHY in the world is this happening?  Please 
help!!!

cut and paste below to see the test case:

In[243]:=
\!\(\(Cosh[\(43\ \[Pi]\)\/\@2] + \((1 - Cosh[43\ \@2\ \[Pi]])\)\ Csch[
            43\ \@2\ \[Pi]]\ Sinh[\(43\ \[Pi]\)\/\@2] // FullSimplify\) //
    N\[IndentingNewLine]
  Cosh[\(43\ \[Pi]\)\/\@2] + \((1 - Cosh[43\ \@2\ \[Pi]])\)\ Csch[
          43\ \@2\ \[Pi]]\ Sinh[\(43\ \[Pi]\)\/\@2] // N\)
Out[243]=
\!\(6.551787517854307`*^-42\)
Out[244]=
\!\(\(-1.9342813113834067`*^25\)\)



thanks,

• Follow-Ups:
  • Re: //N bug, but WHY?
    • From: Andrzej Kozlowski <akozlowski@gmail.com>