No Real Roots Issue

No Real Roots Issue - Mensajes

#1 Publicado: 3/7/2020 9:57:17
ianlh

ianlh

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Hi,

I am a bit stumped with a what is probably a simple problem. I have a root solve in Mathcad that I just cant get to work in Smath, I have tried what I think is correct ways, but still not working, see below for example:
Mcad1.JPG
Smath1.JPG

I have also tried stripping out the units, but still no luck
Hoping someone has the simple solution.
Ian
#2 Publicado: 3/7/2020 13:05:46
Jean Giraud

Jean Giraud

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Always plot before solving !

Solve UNK.sm (212,45 KiB) descargado 1148 vez(es).
#3 Publicado: 3/7/2020 19:03:05
overlord

overlord

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Wrote

Hi,

I am a bit stumped with a what is probably a simple problem. I have a root solve in Mathcad that I just cant get to work in Smath, I have tried what I think is correct ways, but still not working, see below for example:
Mcad1.JPG
Smath1.JPG

I have also tried stripping out the units, but still no luck
Hoping someone has the simple solution.
Ian


I have tried on Mathcad and it didn't work either.
Obviously there is a mistake with the formula.
You can't add kg*N/s^2 with kg/s^2. Units mismatch.
But if you divide the givens you can get the correct answer.
If this approach is true of course since we don't have more information.

Regards.

correct.png
#4 Publicado: 3/7/2020 21:37:54
overlord

overlord

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Jean, direct question;
Are you being sarcastic about my comment?
#5 Publicado: 4/7/2020 9:14:08
Jean Giraud

Jean Giraud

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Wrote

Jean, direct question;
Are you being sarcastic about my comment?


I have removed my comment.
In my times, maths were unitless working well.
Now, put units in maths ... red results.
#6 Publicado: 4/7/2020 15:00:31
Alvaro

Alvaro

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Wrote

Hi,

I am a bit stumped with a what is probably a simple problem. I have a root solve in Mathcad that I just cant get to work in Smath, I have tried what I think is correct ways, but still not working, see below for example:

I have also tried stripping out the units, but still no luck
Hoping someone has the simple solution.
Ian



Hi. Your setup is correct for Mathcad, but unfortunately SMath's solvers do not works like in Mathcad, and needs some help for use units.

SolveWithUnits.sm (16,17 KiB) descargado 1141 vez(es).

Clipboard02.gif

Best regards.
Alvaro
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Вячеслав Мезенцев 4/7/2020 15:43:00, frapuano 5/7/2020 3:18:00, sergio 5/7/2020 12:07:00
#7 Publicado: 4/7/2020 16:16:18
overlord

overlord

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I have checked with changing all inputs;
somehow the two formula give same calculation every time.

Regards

correct2.png
#8 Publicado: 5/7/2020 7:29:58
ianlh

ianlh

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Hi All,

Thanks for the help with this, I like the solution by Alvaro, seems the most elegant.
#9 Publicado: 5/7/2020 10:14:25
Jean Giraud

Jean Giraud

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Unless you don't agree with yourself, solving SQRT implies the two solutions.
Presumably delimiting the range of the solvable project.

SQRTsolve.PNG
#10 Publicado: 5/7/2020 14:30:31
Alvaro

Alvaro

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Wrote

I have checked with changing all inputs;
somehow the two formula give same calculation every time.

Regards



Hi Overlord. You found an amazing symbolic solution for the original problem. I can't explain why, but my guess is that f1, f2 and f3 must to be related with the directors cosines or something like that.

Maple shows that your solution and the symbolic solution are the same, but must to force some "not-always-true" reductions in maple, with the command "maple(simplify(expression,symbolic))"

SolveWithUnits overlord.sm (35,13 KiB) descargado 1170 vez(es).
SolveWithUnits overlord.pdf (97,32 KiB) descargado 800 vez(es).

Best regards.
Alvaro.

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overlord 15/7/2020 17:54:00
#11 Publicado: 6/7/2020 4:43:09
Martin Kraska

Martin Kraska

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Once Maxima and the Maxima plugin are installed, you have a symbolic solver without unit issues.

solve.png
solve.sm (9,99 KiB) descargado 1139 vez(es).
Technische Mechanik mit SMath Studio: https://link.springer.com/book/10.1007/978-3-658-50592-9
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Alvaro 6/7/2020 12:50:00
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