wrong mixed second derivateves

#1 Опубликовано: 25.06.2012 04:17:37

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Hello,

Look at this please
[MATH=eng]f:el(x,1)^3+el(x,2)^3[/MATH]

This is correct:
[MATH=eng]diff(diff(f,el(x,1)),el(x,2))=0[/MATH]

But this is obviously wrong:
v0.95
[MATH=eng]diff(diff(f,el(x,2)),el(x,1))=-el(x,2)*(-1+el(x,2))[/MATH]

It seems that is still present in v.90 as well:
v0.90
[MATH=eng]diff(diff(f,el(x,2)),el(x,1))—-(-1+el(x,2))*el(x,2)[/MATH]

In v0.89.8 you will get the right answer - zeros for both mixed derivatives.

Regards,
Radovan

When Sisyphus climbed to the top of a hill, they said: "Wrong boulder!"

#2 Опубликовано: 30.07.2012 03:14:57

Radovan Omorjan

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Hello,

This is still present in 0.95 build 4594 (30 July 2012).

Any comments?

Regards,
Radovan

When Sisyphus climbed to the top of a hill, they said: "Wrong boulder!"

#3 Опубликовано: 30.07.2012 18:59:59

Davide Carpi

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Hi omorr,

Wrote
Hello,

This is still present in 0.95 build 4594 (30 July 2012).

Any comments?

Regards,
Radovan

I confirm!

seem related to the symbolic simplification (see the attachments)

regards,

w3b5urf3r

derivatives_debug.sm (36 КиБ) скачан 70 раз(а).

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Radovan Omorjan 31.07.2012 01:55:00

#4 Опубликовано: 08.10.2012 19:26:09

Davide Carpi

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Here some (probably) related issues.

best regards,

w3b5urf3r

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#5 Опубликовано: 10.10.2012 16:33:54

Ruben Sidranski

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It's the way SMath handles/prioritizes ASCII characters. I ran into a similar issue with MathCAD. In this case, the second variable of "x" (in the equation) has to be the first variable of the first derivative as shown in w3b5urf3r's screen shot.

#6 Опубликовано: 03.05.2013 16:11:41

Radovan Omorjan

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Hello,

I must be boring with this

, but I think there is neither solution nor satisfactory explanation of this "glitch" regarding second derivatives.
Still present in 0.96

Regards,
Radovan