Difference between symbolic and numeric calculation on imaginary unit

Difference between symbolic and numeric calculation on imaginary unit - Expression (1/i)*(1/i) , symbolic result "1", numeric result "-1" - Messaggi

#1 Pubblicato: 28/11/2012 05:11:37
Gossage

Gossage

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Hello,

I try to calculate "(1/i)*(1/i)" either in symbolic and numeric method and I get "1" and "-1" respectively.

Note that this problem does not appear with the expression "(1/i^2)".

In attachment a simple .sm file to illustrate the bug.

Best regards,
Gossage
bug_imag.sm (2,37 KiB) scaricato 1439 volta(e).
#2 Pubblicato: 28/11/2012 12:57:33
Radovan Omorjan

Radovan Omorjan

325 apprezzamenti e 1 disapprezzamenti in 2.052 post.

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Hello Gossage,

I just can confirm this.
Have no explanation of this, except that this is definitely a bug.

Regards,
Radovan
When Sisyphus climbed to the top of a hill, they said: "Wrong boulder!"
#3 Pubblicato: 28/11/2012 18:49:45
Diego Jarrín

Diego Jarrín

7 apprezzamenti in 14 post.

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There are other problems with the symbolic interpretation.
Did you tried to compute sin(-4*pi/3) and sin(2*pi/3) in the numeric and symbolic methods?
symbolictrouble.sm (17,55 KiB) scaricato 1412 volta(e).
Ecuadorian Electronic engineer and MBA student at Salesian Polytechnic University.
#4 Pubblicato: 29/11/2012 17:11:21
Martin Kraska

Martin Kraska

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Hi

These examples just illustrate the known fact that the SMath symbolic engine is unreliable. Currently, it is not safe to use it. The Numeric engine seems to be more reliable, thus it's usage can be recommended.

What to do if you need symbolic calculations? There is a plugin that communicates with a dos version of maple and is much more powerful than the SMath internal engine. However, the plugin is not localization-safe, i.e. if argument delimiter is set to semicolon ;

I would like SMath to be an 2D document interface to maxima, which has all the math (including units) one would need but lacks the MathCad like document interface.

Best regards, MK
Technische Mechanik mit SMath Studio: https://link.springer.com/book/10.1007/978-3-658-50592-9
#5 Pubblicato: 30/04/2013 18:18:04
Andrey Ivashov

Andrey Ivashov

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Fixed.
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Radovan Omorjan 30/04/2013 18:21:00
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