How to solve these types of equations

How to solve these types of equations - Messages

#21 Posted: 4/19/2021 4:43:29 PM
Martin Kraska

Martin Kraska

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Maxima's solve seems to provide multiple yet not all solutions.

nonlinear_kr.png
nonlinear_kr.sm (8 KiB) downloaded 57 time(s).
Martin Kraska Pre-configured portable distribution of SMath Studio: https://en.smath.info/wiki/SMath%20with%20Plugins.ashx
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Tuan Nguyen 4/20/2021 2:19:00 AM
#22 Posted: 4/19/2021 5:02:46 PM
overlord

overlord

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Wrote

Maxima's solve seems to provide multiple yet not all solutions.


Interesting, cause maxima in linux terminal can find all solutions.
I have tried, wxMaxima (gui of maxima) can also find all of them.

2021-04-19_22-57.png

Wrote

Hello,

It should be careful if the equations are a bit more complicated.

As far as I know, al_nleqsolve() is the only solver in SMath which will solve nonlinear equations in a pure numerical fashion (excluding solvers from Maxima and Maple plugins).

This "numerical thing" was mentioned here many times - maybe to many.

Regards,
Radovan


This is a good demonstation, thanks for your reply.
Since he choose a nickname "newbie" I wanted to keep it simple.
There are a lot of solver in smath, all with their pros and cons.
Which is a good thing I guess, diversity is golden.
If you can't find a solution with a function try another one.
Trying through simpler to complex is the proper way, at least this is my opinion.

Regards
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Tuan Nguyen 4/20/2021 2:19:00 AM
#23 Posted: 4/19/2021 5:36:25 PM
overlord

overlord

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Maxima's solve seems to provide multiple yet not all solutions.


Could you please set optimization to symbolic, expand the matrix, then set to none again?
Maxima may have found all solutions but can't show because of matrix reduced view.
Three dot to expand matrix doesn't appear if optimization is selected to none.
This is a cosmetic bug if I had to make a statement.

Regards

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Martin Kraska 4/20/2021 5:46:00 PM
#24 Posted: 4/19/2021 7:59:16 PM
Jean Giraud

Jean Giraud

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Wrote

Maxima's solve seems to provide multiple yet not all solutions.


FindRoots is sensible to initial, like any other solvers.
Thus a good practice to let it breath by itself from initial
... then collect from visual sanity plot SS 6179.

FindRoots.PNG


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Tuan Nguyen 4/20/2021 2:19:00 AM
#25 Posted: 4/20/2021 4:06:05 PM
Tuan Nguyen

Tuan Nguyen

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Wrote

If I have two non-linear equations with 2 unknowns x,y: f(x,y)=0 and g(x,y)=0. I know there are real roots and the ranges of the roots. How can I solve these in Smath?



1.f(x,y)=0 and g(x,y)=0 are implicit [= 0] in mathematical definition.
2. That they have real roots, you can't know in advance.
3. Solving in there means solving for their intersection
4. Visit this triplet solved.
Cheers ... Jean ... give your functions..

Contour SOLVE AstroidHyperbola.sm (22 KiB) downloaded 66 time(s).



Thank you Jean. Please see attached my smath file. I tried all options but all gave me errors. The current one didn't give me any errors but took forever to solve (or ever able to solve it).Complex Equations.sm (47 KiB) downloaded 52 time(s).
#26 Posted: 4/20/2021 5:46:00 PM
Martin Kraska

Martin Kraska

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Wrote

Wrote

Maxima's solve seems to provide multiple yet not all solutions.


Could you please set optimization to symbolic, expand the matrix, then set to none again?
Maxima may have found all solutions but can't show because of matrix reduced view.
Three dot to expand matrix doesn't appear if optimization is selected to none.
This is a cosmetic bug if I had to make a statement.

Regards



You are right, there seems to be a display bug. Thank you for pointing this out.

Optimization None doesn't properly co-operate with result ellipsis mechanism.
The resize handle is missing.

This is bad in two ways. First, you can't change the amount of displayed elements, second, you can't even see that there are suppressed elements.

nonlinear_kr1.png
nonlinear_kr1.sm (21 KiB) downloaded 54 time(s).
Martin Kraska Pre-configured portable distribution of SMath Studio: https://en.smath.info/wiki/SMath%20with%20Plugins.ashx
#27 Posted: 4/20/2021 7:35:57 PM
Jean Giraud

Jean Giraud

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Thank you Jean. Please see attached my smath file. I tried all options but all gave me errors. The current one didn't give me any errors but took forever to solve (or ever able to solve it)


Try to plot something as soon as possible.
Here, it computes in few seconds but complains
too many not defined, units don't match, result above max ...
#28 Posted: 4/21/2021 8:41:04 AM
Jean Giraud

Jean Giraud

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Try to plot something as soon as possible.
Here, it computes in few seconds but complains
too many not defined, units don't match, result above max ...



MonsterBig.PNG

Complex Equations (1 to be doctored).sm (59 KiB) downloaded 49 time(s).
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Tuan Nguyen 4/21/2021 12:42:00 PM
#29 Posted: 4/21/2021 11:36:50 AM
Jean Giraud

Jean Giraud

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.... download this same updated in split part.
At this point make the Units match.
I don't doctor units, they are against maths and my conviction.
Keep working hard ... Jean

Complex Equations (1 to be doctored).sm (64 KiB) downloaded 58 time(s).
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Tuan Nguyen 4/21/2021 12:42:00 PM
#30 Posted: 4/21/2021 12:45:01 PM
Tuan Nguyen

Tuan Nguyen

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.... download this same updated in split part.
At this point make the Units match.
I don't doctor units, they are against maths and my conviction.
Keep working hard ... Jean

Complex Equations (1 to be doctored).sm (64 KiB) downloaded 58 time(s).



Thanks, Jean for giving this a stab. Let me try to remove all the units in the equations and see what happens.
#31 Posted: 4/21/2021 1:09:42 PM
Tuan Nguyen

Tuan Nguyen

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Wrote

.... download this same updated in split part.
At this point make the Units match.
I don't doctor units, they are against maths and my conviction.
Keep working hard ... Jean

Complex Equations (1 to be doctored).sm (64 KiB) downloaded 58 time(s).



Please use the attached file. No more units in the equations. Or use this block
Block to remove units in the equationsComplex Equations (unitless).sm (50 KiB) downloaded 60 time(s).
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