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Offline Joey Ooi  
#1 Posted : 23 May 2017 00:28:13(UTC)
Joey Ooi

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The integral of 1/(ln(x) with limits of x from 2 to 1000 does not agree with mathlab or maxima --
The numerical value of the following integration is off -- should be 176.56 and Smath gives 177.1
Any idea what could be the problem?
Thanks
Joey Ooi

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Offline Davide Carpi  
#2 Posted : 23 May 2017 00:50:40(UTC)
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Hello Joey Ooi Offline ,

You have to set a better accuracy in the global options (tools >> options >> calculation)

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Offline Joey Ooi  
#3 Posted : 23 May 2017 03:32:54(UTC)
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Thank you for your quick and accurate response Davide.
It was very helpful indeed.
Best regards
Joey
Offline Jean Giraud  
#4 Posted : 23 May 2017 13:53:55(UTC)
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Originally Posted by: Joey Ooi Go to Quoted Post
Any idea what could be the problem?


Smath Simpson iterative integrator is known to range from
exact [sometimes] to poor. Increasing accuracy is fine in
this example but will not converge in other instances like
in the Fourier Quantum double integral. You can rescue
your example using the attached Romberg.
Mathematica online integrator link added.

Jean

Integrate Mathematica.sm (10kb) downloaded 26 time(s).



Offline Jean Giraud  
#5 Posted : 23 May 2017 14:37:48(UTC)
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... revisit same work sheet for the 7 decimals !

Jean

Integrate Mathematica.sm (11kb) downloaded 18 time(s).
Offline Jean Giraud  
#6 Posted : 23 May 2017 14:53:58(UTC)
Jean Giraud

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... like this

Romberg Integrator.gif
Offline Jean Giraud  
#7 Posted : 23 May 2017 20:32:33(UTC)
Jean Giraud

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How many numerical integrators have been imagined ?
1+1+1+... Even Mathcad aren't so easy to deal with.
This visit is worth the time spent.

Jean

Fourier Quantum CoC Model.sm (37kb) downloaded 17 time(s).
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