Difference between symbolic and numeric calculation on imaginary unit

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

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Gossage		#1 Posted : 28 November 2012 12:11:37(UTC)
Rank: Newbie Groups: Registered Joined: 28/11/2012(UTC) Posts: 1		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 Edited by moderator 01 May 2013 01:18:14(UTC) \| Reason: Not specified* File Attachment(s): bug_imag.sm (3kb) downloaded 24 time(s).


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omorr		#2 Posted : 28 November 2012 19:57:33(UTC)
Rank: Administration Groups: Registered, Advanced Member Joined: 23/06/2009(UTC) Posts: 1,740 Was thanked: 318 time(s) in 268 post(s)		Hello Gossage, I just can confirm this. Have no explanation of this, except that this is definitely a bug. Regards, Radovan
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Jarrinator		#3 Posted : 29 November 2012 01:49:45(UTC)
Rank: Member Groups: Registered Joined: 15/05/2012(UTC) Posts: 14 Location: Profeta Miqueas Oe10-309 y Tabiazo Was thanked: 7 time(s) in 4 post(s)		There are other problems with the symbolic interpretation. Did you tried to compute sin(-4pi/3) and sin(2pi/3) in the numeric and symbolic methods? Edited by user 29 November 2012 01:52:11(UTC) \| Reason: Not specified File Attachment(s): symbolictrouble.sm (18kb) downloaded 39 time(s).
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mkraska		#4 Posted : 30 November 2012 00:11:21(UTC)
Rank: Advanced Member Groups: Registered Joined: 15/04/2012(UTC) Posts: 1,986 Was thanked: 1124 time(s) in 721 post(s)		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
		Martin Kraska Pre-configured portable distribution of SMath Studio: https://smath.com/wiki/SMath_with_Plugins.ashx


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Andrey Ivashov		#5 Posted : 01 May 2013 01:18:04(UTC)
Rank: Administration Groups: Developers, Registered, Knovel Developers, Administrators, Advanced Member Joined: 11/07/2008(UTC) Posts: 1,616 Was thanked: 1978 time(s) in 666 post(s)		Fixed.
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1 user thanked Andrey Ivashov for this useful post.		on 01/05/2013(UTC)
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