For the following program using dsolve to solved a differential equation with a sum of exponential inputs, the time required has a huge dependence on subtle difference in paramters.

For example, if Cl := 0.32, calculation time is 1.4 sec.    If Cl := 0.33,  calculation time is 39 sec.

Also, calculation time seems to have huge dependence  on whether or not I truncate M

Can someone please explain what is going on?

restart;
st := time();
N := 4;

T := 5.0/60;
M := 6905;
dose := t -> M*sum(Heaviside(t - 24*k/N)*exp((-t + 24*k/N)/T), k = 0 .. 2*N - 1);
Cl := 0.32;
deq := diff(C(t), t) = dose(t) - Cl*C(t);
sol := t -> rhs(dsolve({deq, C(0) = 0}));
p := plot(sol(t), t = 0 .. 48);
time() - st;
                             1.360
 

Hi,

I am the administrator of Maple in my school, and all the students use Maple in part of their exams. Is it possible  to block the access to ChatGPT thru eg. the firewall or otherwise during exams. 

The reason for this question is that the students must have access to some internet sources during exams, but definately not CharGPT.

Kind regards 

Per Kirkegaard

Hello, I try to solve the equations of the odometric model with the Maple 2024 but I have not the answers as with the hands, can you help me to verify it ?

dsolve(diff(phi(t), t) = tan(10*t)/5)

dsolve(diff(x(t), t) = V*cos(ln(1 + tan(10*t)^2)/100))

dsolve(diff(y(t), t) = V*sin(ln(1 + tan(10*t)^2)/100))

Best regards, Edern Ollivier.

I noticed that Student:-ODEs:-ODESteps does not use the newer subscripted constant of integrations for solution of odes which looks much nicer.

Is there a way to make it use same constant of integrations as dsolve() does? Compare  

This is on a worksheet using typesetting level extended. Worksheet is attached

Download make_step_solution_use_new_constant_of_integration.mw

Is there a way to disable Maples AI Formula Assistant? This could be relevant when using Maple for a test.

I found that sometimes Maple gives

               Error, (in Typesetting:-Parse) too many levels of recursion

When using the Latex command on the output of Student:-ODEs:-ODESteps

Below is worksheet showing it works for some and gives error for others. Is there a workaround for this? I'd like to convert the steps to Latex.

This happens in worksheet using either Display->Typesetting level as EXTENDED or STANDARD

Download latex_error_ODE_steps_maple_2024_april_13_2024.mw

update: Reported to Maplesoft support.

I have a proceure that returns 7 values. I cac get it to return ang single specific value ousing e.g [2] to get the second.
Or a range[3..6] for the third to sixth.

Is there a way to get specific seperated values e.g [1] and[[6]. The procedure is burried in a package so it is difficult to post.

This second order (Euler type) ode has no solution for the given two initial conditions. but Maple gives solution with one unresolved constant of integration.

ode:=x^2*diff(y(x),x$2)-2*y(x)=0;
ic:=y(0)=4,D(y)(0)=-1;

sol_no_IC:=dsolve(ode)

The IC's are given at x=0 as a trick to see what Maple will do. We see that at x=0 there is division by zero. So no solution exist for these IC's. But see what happens

sol_with_IC:=dsolve([ode,ic])

It seems Maple simply threw away the part of the solution it could not handle due to the x=0 and just returned the rest.

odetest(sol_with_IC,[ode,ic])

The correct answer should have been the NULL solution (i.e. no solution). 

What Am I missing here? Why does Maple do this? Should Maple have returned such a solution?

Maple 2024 on windows 10.

update:

Reported to Maplesoft support.

update:

Here is another example ode. This is first order ode. Maple gives a solution that does not satisfy the initial condition also. I wish I can understand how Maple comes up with these solutions since when I solve these by hand I see it is not possible to satisfy the IC, hence no solution exist.

Download another_strange_solution_ode_maple_2024.mw

I have a simple tank design worksheet that calculates dimensions of a tank that I need to build to hold a given amount of liquid.  My question is this - when I include a "with(Units);" statement, the volume function gets rendered in operator prefix notation.  Why is this?  Is there a setting to prevent this from happening?  Thanks.

Without "with(Units);"...

With "with(Units);"...

I've included a worksheet that shows the function both with and without the inclusion of "with(Units);".

Tank_Design_Calculation_-_Units_Question_(v00).mw

I have two expressions, wo_theta and with_theta, which depend on multiple variables.

I would need your help to:

1. Verify, as formally as possible, that wo_theta > with_theta always, i.e., for any value of theta different from zero (and regardless of the values taken up by the other variables)
2. Show the above in a way that is easy and immediate to interpret (perhaps using some type of plot?)

In other words, I want to verify that as soon as I introduce any theta in my expression such expression becomes smaller:

Download inequality.mw

I have a problem with the order  of the Eigenvalues and Vectors flipping. It is a bit random. I only found it trying to understand why a procedure sometimes rotated a conic one way and  then the other. This a really causing a quite a problem, I have only tried this in Maple 2024 so far. I have included screen shots to prove the effect.

Download 2024-03-21_Q_Eigenvector_output_flipping.mw

I do not know if this caused by same crash in Reproducible--Server-Crash-Kernel-Connection-Has-Been-Lost  or not.

Could someone be able to find out? It happens each time the code is run on windows 10. 

Download another_server_crash_on_int_maple_2024_april_4_2024.mw

ps. reported to Maplesoft.

The above is new crash in Maple 2024. Below shows no crash in Maple 2023:

Download int_on_maple_2023.mw

Update:

Here is a movie showing the crash. It also happens from the command line. All on windows 10.

My ini file has  nothing in it, other than one command which prints the process ID which I had there for over a year now.  This is after restarting Maple fresh and nothing else running other than this one worksheet.

Here is movie showing the crash from command line also. On windows 10 pro.

I just discoverd today the step solutions for series in Student package 

Now i try to solve this with my own steps here ..

Note: was not capable to get a closed form?

Download Het_Basel_Probleem_van_Euler.mw

@ecterrab

Fetching package "Physics Updates" from MapleCloud...

ID: 5137472255164416
Version: 1713
URL: https://maple.cloud

An error occurred, the package was not installed:
Could not open workbook: /tmp/cloudDownload3108059082303936092/Physics Updates_1712064079729.maple

Same problem on Maple 2024 for Windows and Linux!!!

The following is a simple example of what I would like to do: 

M := Array(1 .. 10, 1 .. 2);

for i to 10 do
    M[i, 1] := i;
    M[i, 2] := 3*i;
end do;

Mt := Interpolation:-LinearInterpolation(M);
E := t -> Mt(t);
diffeq := D(C)(t) = E(t);
dsolve({diffeq, C(0) = 0}, {C(t)}, numeric);
Error, (in dsolve/numeric/process_input) unknown Interpolation:-LinearInterpolation([Vector(10, [1.,2.,3.,4.,5.,6.,7.,8.,9.,10.], datatype = float[8], attributes = [source_rtable = (Vector(10, [1.,2.,3.,4.,5.,6.,7.,8.,9.,10.], datatype = float[8], attributes = [source_rtable = (Array(1..10, 1..2, [[1.,3.],[2.,6.],[3.,9.],[4.,12.],[5.,15.],[6.,18.],[7.,21.],[8.,24.],[9.,27.],[10.,30.]], datatype = float[8]))]))])],Vector(10, [3.,6.,9.,12.,15.,18.,21.,24.,27.,30.], datatype = float[8], attributes = [source_rtable = (Array(1..10, 1..2, [[1.,3.],[2.,6.],[3.,9.],[4.,12.],[5.,15.],[6.,18.],[7.,21.],[8.,24.],[9.,27.],[10.,30.]], datatype = float[8]))]),uniform = true,verify = false) present in ODE system is not a specified dependent variable or evaluatable procedure