## Solve the resistor grid of 1 ohm. 3*4*5 Rubik cub...

Resistor grid of one ohm to make rubik cube of 3*4*5.
Resistance of red node to node is

nx, ny, nz;

Ans := R3D;
Ans*Unit('ohm');
3, 4, 5

1.211 Unit(&Omega;)

Tokoro.

## Solve the resistor grid of 1 ohm. ...

R1 - R31 resistance is 17/11 ohm. (Top to bottom)

R1 - R2 resistance is 16273/25080 ohm. ( Each one element's node to node)

Can any one solve these Electric Circuit?

Tokoro.

## Annoying little thing with Greeks letters . Known ...

Hi !

I just noticed a strange behavior of Maple with Greek letters.
I have Maple 2017 and 2018 on Windows 10 .

Suppose you write a procedure that contains Greek letters.

If you run the procedure definition, the Greek letters are not displayed correctly.
They will be displayed in words: alpha, beta, gamma,...
The procedure will still work.

Now close the file. Then open this file. Maple now shows you the procedure with the Greek letters correctly displayed.

I added a file as an example.
Maybe it's an annoying little problem known for a long time ? I don't know .
I have an old version of Maple V Release V (1997) which does not have this problem.

Best regards !

alphabeta.mw

## i want to find best equation with nonlinear fit or...

i want to find best equation with nonlinear fit or fit for my result
my first variable in column one with name h
my second variable in column two with name d
my result in the column 3

i just know that my ratio to b is exponential

Matrix(20, 3, [[70, 8, 8.468140006], [70, 10, 4.105515432], [70, 12, 2.36261199], [70, 14, 1.422093923], [70, 16, 0.9], [100, 8, 20.47249229], [100, 10, 9.618450629], [100, 12, 5.360869165], [100, 14, 3.399312905], [100, 16, 2.640399788], [130, 8, 35.90466304], [130, 10, 17.62958097], [130, 12, 9.828362586], [130, 14, 5.866863694], [130, 16, 3.799262645], [160, 8, 57.31814648], [160, 10, 34.49692774], [160, 12, 15.39340528], [160, 14, 9.991012951], [160, 16, 6.049343013]]);

how can i get best equation with ninlinearFit

thant you so much

i also show my result in below plot

## Is the LinearAlgebra command GenerateMatrix Improp...

I am using GenerateMatrix to construct a matrix out of a set of 6 equations with 6 variables.  The output of Generate Matrix is not sorted correctly.  Where am I going wrong? Is this a bug?

The command GenerateMatrix is not sorting my set of equations properly.

Define a set of 6 equations.

 (1)

This is what each one looks like individually.

 (2)

 (3)

 (4)

 (5)

 (6)

 (7)

The variables used in the above set of equations.

 (8)

 (9)

 (10)

This output seems wrong because a row of zeros appears in .  The first entry of the column vector contains the full equation. Thus, it seems GenerateMatrix didn't sort the set of equation properly.  I tried re-writing the  offending equation  as ,but maple just changes it back on evaluation.

I think the output should look like:

I rename the matrix and column vector and use LinearSolve to find a solution for T.

 (11)

 (12)

 (13)

## how to declare 'd' as a const...

Hello

I want to declare 'd' as a constant.

Please tell me how to declare 'd' as a constant.

## intersection de deux droites dans l'espace...

intersection de deux droites l1 et l2 telles que l1 sous forme parametrique est [57/5 + 20*t, -21/5 - 40*t, 20*t] et de la meme façon

l2 [249/100 - 120*t, 471/100 - 80*t, 200*t]. t est le parametre  . maple donne pour l'intersection de l1 et l2 le point P de coordonnes

[249/100, 471/100, 0] que je ne trouve pas .expliquez moi ce resultat et merci beaucoup.

## How to ransfer computed quantities between workshe...

I have a big matrix which is computed in a worksheet, now I have to use this matrix in another worksheet. Could you recommend some ways of healthy transferring of quantities between worksheets?

## how to connect the components of electrical digita...

here is logical_circuit.msim

i cannot connect the output of the left two AndGates to the input of the right AndGate. They are both digital signal connectors, why cannot be connected?

## Changing symbols in matrixplot...

```with(plots);
with(LinearAlgebra);
A := Matrix([[2, 1, 0, 0, 3], [0, 2, 1, 0, 0], [0, 0, 2, 1, 0], [0, 0, 0, 2, 1], [0, 0, 0, 0, 2]]);
sparsematrixplot(A, matrixview, color = "Red", symbol = "cross");```

How do I change the plot to show other symbols? Even though I write for example "cross" I still get the default box.

Also, is there a way in which I can let the color depend on the number in the matrix? Right now it just shows all non-zero entries.

restart:
digits := 20;
unprotect(D);
G := 0.04361098108*x^2 + 0.4810001561*x*y + 1.326278064*y^2 - 0.7320831383*x - 2.656083763*y + 1 = 0
f := (x, y) -> lhs(G);
coeffs(f(x, y));
A, B, C, D, E, F := coeffs(f(x, y));
A := coeff(f(x, y), x, 2);
B := coeff(coeff(f(x, y), x), y);
C := coeff(f(x, y), y, 2);
D := coeff(coeff(f(x, y), x, 1), y, 0);
E := coeff(coeff(f(x, y), y, 1), x, 0);
F := tcoeff(f(x, y));
expand(B^2 - ((4*A) . C));
digits := 20

f := proc (x, y) options operator, arrow; lhs(G) end proc

1, -0.7320831383, 1.326278064, 0.04361098108, 0.4810001561,

-2.656083763

A, B, C, D, E, F := 1, -0.7320831383, 1.326278064, 0.04361098108,

0.4810001561, -2.656083763

A := 0.04361098108

B := 0.4810001561

C := 1.326278064

D := -0.7320831383

E := -2.656083763

F := 1

0.

with(geometry):
_EnvHorizontalName := 'x': _EnvVerticalName := 'y':
conic(co,f(x,y),[x,y]):
detail(co);
/
GeometryDetail\["name of the object", co],
["form of the object", ellipse2d],
["center", [1.212351672 ^(10, 10), -2.198412833 ^(10, 9)]],
["foci", [[2.424703344 ^(10, 10), -4.396825668 ^(10, 9)],
[0.1787052775, 0.9855002601]]],
["length of the major axis", 2.464245740 ^(10, 10)],
["length of the minor axis", 66579.62094],
[                                               2
["equation of the ellipse", 1. + 0.04361098108 x
2
+ 0.4810001561 x y + 1.326278064 y  - 0.7320831383 x
]\
- 2.656083763 y = 0]/;
"_noterminate";

G is a parabola with B^2-4*A*C=0 or an ellipse ? A =1 or F=1 ? Thank you for youy answer.

## How to find the Lie symmetry Infinitesimals of the...

I need the Infinitesimals(Lie group analysis) of the system of PDE. I have attached below the system of PDE in MAPLE given below.MAPLE_Help.mw

Thank you

## what causes Error, `DEtools` does not evaluate to ...

I have code which in module which does this

DEtools:-kovacicsols(ode,func)

Where ode is some ode and func is y(x).  When I step in the debugger, I get exception at this. It says

DBG> DEtools:-kovacicsols(ode,func)
Error, `DEtools` does not evaluate to a module

Same exact code works OK from worksheet as expected.   SO for some reason, inside this module it does not see DEtools and I have no idea why.

Then I tried with :-  before DEtools, but this did not help. it gives

DBG> :-DEtools:-kovacicsols(ode,func)
Error, `table([(dperiodic_sols)=proc () `DEtools/init`() <> 0; `ODEtools/intfactor`(_passed); end etc...
` does not evaluate to a module

In a worksheet, it all works OK

ode:=diff(diff(y(x),x),x) = (-3/16/x^2-2/9/(x-1)^2+3/16/x/(x-1))*y(x);
func:=y(x);
DEtools:-kovacicsols(ode,func)

Gives the solution with no error.

Any suggestion what could be the cause and what to try next? I never seen anything like this. I am running this code using

interface(warnlevel=4);
kernelopts('assertlevel'=2):

I am able to make a MWE. It seems this always happens in the debugger.  But if  I let it run, it works somehow. Only when I try to step into it, it gives error. Here is MWE

```interface(warnlevel=4);
kernelopts('assertlevel'=2):
foo:=proc(ode,func)
local result;
DEBUG();
result:=DEtools:-kovacicsols(ode,func);
return result;
end proc;
```

And now

```ode:=diff(diff(y(x),x),x) = (-3/16/x^2-2/9/(x-1)^2+3/16/x/(x-1))*y(x);
func:=y(x);
foo(ode,y(x))
```

Now in the debugger if I do DEtools:-kovacicsols(ode,func) or if I stepin the call, I get the error. But I hit the continue botton, I do not get the error and it gives solution.

Why this happens?

Maple 2021.2 on windows 10

## how does the "edge with init" in boolean of signal...

as the cuts show,  i build a simple  system to check how does the "edge with init" work? The switch is "ideal opening switch". the rising edge is always "0" while the voltage is always 1v, it seems that the "edge with init" doesn't work. Please give me some explaintion of the problem.

here is thetest.msim

## Calling UMFPACK sparsedirect linearsolver using on...

@acer,
In the past, you had shown how to use take a given sparse A matrix and store the LU components and use the same factorization for multiple backsolves at https://www.mapleprimes.com/posts/41191-Solving-Sparse-Linear-Systems-In-Maple#comment200817

When PDEs are solved, we are calling the A matrix at every time step (with some discretizations in x) and the factorization is done and stored at every time step (this is time-consuming and memory-consuming). Is it possible to call UMFPACK using only the sparse storage and entries? The main routine seems to provide the option

https://people.sc.fsu.edu/~jburkardt/f77_src/umfpack/umfpack.html

This would mean that the pattern is found only once for the Jacobian at t= 0, then only the non-zero sparse entries (vector/row, not a matrix) are updated at every time step.

To be clear, what I am asking for is create a random sparse matrix (say 4x4 or 10x10)
create a b Vector.

Solve AZ =b with method = SparseDirect. (This should internally create and store R, CC, X as at https://people.sc.fsu.edu/~jburkardt/f77_src/umfpack/umfpack.html)

Store R, CC, X and update only X for a different A matrix with the same sparsity pattern and solve for Z using stored (R, CC), and updated X.

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