## Is my system of equations unsolvable?...

Hi.

I'm working on an electronics project currently. In that project I have been trying to solve a system of inequalities, as shown by the picture from Maple below:

restart;

R__1 := 1;
lign1 := V__i/(R__4*(1/R__1 + 1/R__2 + 1/R__3 + 1/R__4)) = C*(k__1 - R/R__C + R);
lign2 := V__i*(1/R__1 + 1/R__4)/(1/R__1 + 1/R__2 + 1/R__3 + 1/R__4) = C*(k__2 - R/R__C + R);
lign3 := V__i*(1/R__2 + 1/R__4)/(1/R__1 + 1/R__2 + 1/R__3 + 1/R__4) = C*(k__3 - R/R__C + R);
lign4 := V__i*(1/R__3 + 1/R__4)/(1/R__1 + 1/R__2 + 1/R__3 + 1/R__4) = C*(k__4 - R/R__C + R);
lign5 := V__i*(1/R__1 + 1/R__2 + 1/R__4)/(1/R__1 + 1/R__2 + 1/R__3 + 1/R__4) = C*(k__5 - R/R__C + R);
lign6 := V__i*(1/R__1 + 1/R__3 + 1/R__4)/(1/R__1 + 1/R__2 + 1/R__3 + 1/R__4) = C*(k__6 - R/R__C + R);
lign7 := V__i*(1/R__2 + 1/R__3 + 1/R__4)/(1/R__1 + 1/R__2 + 1/R__3 + 1/R__4) = C*(k__7 - R/R__C + R);
solve({lign1, lign2, lign3, lign4, lign5, lign6, lign7}, [R__4, R__2, R__3, R__C, R, C, V__i]);

Here's a picture as well:

However, the solution is simply that V_i = 0 and C=0, which is not really helping me. Am I doing something wrong here or is my system of equalities simply unsolvabe?

## Interfacing with visual molecular dynamics softwar...

Can you please post the procedure for interfacing maple with visual molecular dynamics (VMD) software. Thank you.

## How to get shift and dual_shift for the same varia...

I want to do the following: Suppose we are given a linear recurrence operator with polynomial coefficients say (n+2)N^2+(2n^2-3n+5)+(n-4) where N is the shift operator with respect to n. I want to apply the following substitution:

(i) N-> (N+1)

(ii) n->n(N^(-1)+1)

and compute the corresponding equation. To do this, I want to use Maple's Ore_Algebra package. However, I could not define N and N^(-1), i.e N inverse, at the same time.

To sum up, I want to get something like

A := Ore_Algebra(shift= [N,n] , dual_shift=[Ninv,n]); however it is not allowed.

## Is there a builtin way to add a Units type to a va...

This should be pretty simple.

    with(Units:-Standard);
local var::Unit(kg);     #generates a warning
var := 1;
var;                     #-> 1 kg... alas this doesn't work (it's just 1)

In other words, I want to declare a variable with an unknown quantity and known Unit at the outset similar to how things are done in C-style languages, and later set the numeric value. The goal is to make it easier to manipulate functions that deal with lots of different physics unit types without having to write them each individual line. For example on lines 10-13 I manually include the units when it would be more convenient if they were already tied to the variable they're associated with.

Solving a simple physics problem to find the radius of a planet with the universal gravitational constant & known density:

I know types exists in Maple, i.e.

    evalfr := proc(expr, iexact::integer := 0)
if   0 < iexact   then  return convert(evalf(expr), rational, iexact);
elif iexact = -1  then  convert(evalf(expr), rational, exact);
else                    return convert(evalf(expr), rational);
end if; end proc

This just being a wrapper with iexact typed as an integer setting up a set of conditionals around evalf to rationalize an expression when using ScientificConstants.

I've considered using anonymous functions to emulate this behavior with setters and getters, but that seems like overkill for something that is probably builtin. For the time being I have configured my worksheet so it references secondary variables,

    var := var2*Unit(kg)

This strikes me as somewhat inelegant. Also trying to use the same variable name in-line (i.e. var := var*Unit(kg)) gives Error, recursive assignment.

I am curious if there is a correct Maple way to do something like this. Or would I have to implement some sort of anonymous function to get the behavior I want? Appreciate any help!

[1]: https://i.stack.imgur.com/ovZSB.png

## Sharing to Maple Cloud with own libraries...

I'm trying to upload a file to Maple Cloud for the first time, but I am getting an error due to the way I use libraries.

The first lines of the startup code in the sheet look like this.

libname := "S:/Maple/NODE_Library", libname;
with(NODETreMaterial);
with(NODETreTverrsnitt);

The libraries are on a network drive on our server.

The question is - how can I solve this? Would it be better to somehow upload those libraries to Maple Cloud (no idea how to do that by the way), or can it be solved in a different way?

## How to prevent debug values displaying in the work...

When executing DEBUG within inline code (not within a procedure) the values displayed in successive debug windows (on clicking continue) are added to the end of my worksheet. How can the latter display be prevented?

## partial differential equation ...

Hello,

is it possible to solve the attached partial differential equation with zero initial boundary condition?

If not by assuming diff(u(sigma, tau, phi, t), t, t)=0 is there an answer for the equation?

Thanks

lapla.mw

## How do I solve my Eqs. in Maple?...

Suppose two following Eqs.:

(1) du/dt+d(u*w)/dx=0

(2) dw/dt+wdw/dx=0

I want to expand u(x,t) and w(x,t) in the power series of epsilon

u=u0+epsilon*u1+epsilon^2*u2+…

w=w0+epsilon*w1+epsilon^2*w2+…

and change the variables x,t to X,T as follows

X=(x-alpha*t) and T=beta*t,

and solving Eqs. (1) and (2) for different order of epsilon (epsilon, epsilon^2, epsilon^3,…) to finding u0,w0,u1,w1,…

How do I do that?

Thanks.

## Maple 2020 offers many improvements ...

Maple 2020 offers many improvements motivated and driven by our users.

## Maple 2018 recently become sluggish to start up ...

Maple 2018  has recently has  become sluggish to start up  -and very slow to respond to input. Can anyone suggest remedies?  I have plenty of space and CPU. Other apps seem to start fine.  Can any suggest a diagnosis and/or solution?

Melvin

## Converting Maple Tutor output to LaTeX...

Maple Tutors allow for copying of MathML but I need LaTeX of it. Any help please?

## How to plot Bloch sphere on maple?...

If we have an equation for the generalized Bloch sphere i.e.,

\partial_{t}(u^{2} + v^{2} + w^{2}) = 0,

where u, v and w are functions of x and t and the initial conditions u=v=0, w=-1. Then how to plot this equation on maple?

## round function...

Being an absolut newbie to Maple I find some of the functions a bit strange and difficult.

One of the things is e.g. rounding numbers.

In Pyton and other languages it is quite simple and straightforward when rounding a number.

round(number, digits)

If you have digits = 0 then you get an integer, otherwise you get a number with the number of digits chosen.

In Maple the round function is just for rounding to an integer.

To round to something else currently I don't really know what I would use. There is the evalf function, which one can use like evalf[digits](number), but that doesn't give you the value with digits. It gives you a number with significant digits, which means, also including the numbers before the comma delimiter.

Python
round(15.76543,2) = 15.77

Maple
evalf[2](15.76543) = 16

Wouldn't it be much easier to expand the functionality of the round function in Maple?

## Maple Companion App Trouble...

"Frame your math" does not work on a new iPhone XS; however, surprisingly, it work just fine on an old iPad (4th gen).

I am logged in. The app has access to the camera. The companion app does allow manual entry of equation to upload to the Maple cloud.

I expect it's something simple--like some sort of permissions setting, but I cannot find it . . .

BTW: The error is "The request timed out. Check your Internet connection."

## Vector issues and Excel .csv ArrayTools Append bug...

Noticed an issue with Vector and excel.  Not even really excel but I found it through that.

If I select a row in excel and do a copy paste into Maple it sometimes appears as if it's a list.  ie it shows up as [1,2,3,4]  other times it shows up as [ 1 2 3 4 ] signifying an array (for this example I've saved as the data under the variable a).  Running whattype(a) on the data shows they're both arrays.  Of course it's probably wise to instead load data through Excel into Maple by using the ExcelTools and Import option, however I didn't think there was no reason to use the copy paste option.  It does, to some extent, or maybe, well, it shows a limitation.

In the first instance when it shows up as a list, I thought it might be simple enough just to add other numbers in the list ie/ just tack on ,5,6,7,8 after the 4.  But after pressing enter we get the error

Error, invalid sequence

I don't understand why I couldn't just add to the copied data but maybe it's the formatting of the data that was pasted into maple?

With the original copied data, I can use with(plots):  listplot(a) no problem however, we want to add data.  ArrayTools will let us Append data to the vector

with(plots):
with(ArrayTools):
Append(a,5,6,7,8)

listplot(a) # will throw another error

Error, (in plots:-pointplot) points cannot be converted to floating-point values (this doesn't show in Maple 2019 but does come up in Maple 18)

For Maple 2019 it with responds with a returned array [ 1 2 3 4 5,6,7,8]

Running listplot on that Appended Array.  Maple only recognizes the next 1 added value.

So this means appending values using ArrayTools and Append only allows us to append one value at a time?  Is that a bug?  Are there better ways to append values to vectors?  The only solution for that is to convert to a list and use op to append more values.  But perhaps Maple should have understood the copied values from Excel should have been a list or listlist of values?

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