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Re: Can't get Mathematica to evaluate correctly a difficult

  • To: mathgroup at smc.vnet.net
  • Subject: [mg111549] Re: Can't get Mathematica to evaluate correctly a difficult
  • From: Peter Pein <petsie at dordos.net>
  • Date: Wed, 4 Aug 2010 07:51:12 -0400 (EDT)
  • References: <i3bd7l$pjr$1@smc.vnet.net>

Am Wed, 4 Aug 2010 09:51:49 +0000 (UTC)
schrieb Damien Wyart <damien.wyart at free.fr>:

> Hello,
> 
> I am using Mathematica 7.0.2 and playing a bit with an expression
> analyzed in the following paper:
> http://www.loria.fr/~zimmerma/papers/cise.pdf
> 
> I tried many constructions with N and SetPrecision and can't get
> Mathematica to output the correct result (I am not very experienced
> with Mathematica). Here is the expression :
> 
> 173746*Sin[10^22]+94228*Log[17.1]-78487*Exp[0.42]
> 
> The correct result should be -1.341818958*10^-12 but even forcing each
> term with N and a very large number, I am still not getting this value
> at all.
> 
> 
> Any help will be appreciated. Thanks in advance ; best regards,
> 

Hi Damien,

use exact input and then evaluate with a precision greater than 22 :

In[14]:= N[173746*Sin[10^22]+94228*Log[171/10]-78487*Exp[21/50],30]
Out[14]= -1.34181895782961954970427868423*10^-12

or change the precision of the input:

In[15]:= 173746*Sin[10^22]+94228*Log[17.1`30]-78487*Exp[0.42`30]
Out[15]= -1.341818957830*10^-12

Peter



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