## 8679 Reputation

11 years, 274 days

## why mapleprimes removes tags from post?...

MaplePrimes

I noticed tags on the post

https://mapleprimes.com/questions/238161-Why-Maple-Gives-Solution-To-Euler-Ode

keep disappearing.

I added tags "differential equation" and "dsolve" and so on.

Later on when I visit this site again I found the tags are all gone.

Why does Mapleprimes remove the tags on post?

Or is someone else removing the tags? If so, why? is something wrong with the tags I've added?

This happend twice on this one post. I noticed earlier today the tags were gone, so I added them again. And now I see the same thing. They are all gone.

## Error, (in Typesetting:-Parse) too many ...

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

 > restart;
 > interface(version);

 > Physics:-Version();

 > ode:=diff(y(x),x)=0; the_output:=Student:-ODEs:-ODESteps(ode,y(x)): latex(the_output)

\begin{array}{ccc}
& {} & \textrm{Let's solve}
\\
{} & {} & \frac{d}{d x}y \! \left(x \right)=0
\\
\textrm{•} & {} & \textrm{Highest derivative means the order of the ODE is}1
\\
{} & {} & \frac{d}{d x}y \! \left(x \right)
\\
\textrm{•} & {} & \textrm{Integrate both sides with respect to}x
\\
{} & {} & \int \left(\frac{d}{d x}y \! \left(x \right)\right)d x =\int 0d x +\mathit{C1}
\\
\textrm{•} & {} & \textrm{Evaluate integral}
\\
{} & {} & y \! \left(x \right)=\mathit{C1}
\\
\textrm{•} & {} & \textrm{Solve for}y \! \left(x \right)
\\
{} & {} & y \! \left(x \right)=\mathit{C1}
\end{array}

 > ode := diff(y(x), x, x, x ) + 3*diff(y(x), x, x) + 4*diff(y(x), x) + 2*y(x) = 0; the_output:=Student:-ODEs:-ODESteps(ode,y(x)): latex(the_output)

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

 >

update: Reported to Maplesoft support.

## Why Maple gives solution to Euler ode wh...

Maple 2024

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.

 > interface(version);

 > Physics:-Version();

 > restart;

 > ode:=diff(y(x),x)+y(x)/x=x^2; ic:=y(0)=a;

 > dsolve(ode)

 > sol:=dsolve([ode,ic])

 > odetest(sol,[ode,ic])

 > Student:-ODEs:-ODESteps([ode,ic])

Error, (in Student:-ODEs:-applyICO1) numeric exception: division by zero

 >

## Another reproducible server crash in Map...

Maple 2024

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.

 > interface(version);

 > Physics:-Version();

 > restart;

 > u:=Int(2/3/alpha^(3/2)*sin(1/2*3^(1/2)*ln(alpha))*sin(alpha)*3^(1/2),alpha = 0 .. x)

 > value(u);

ps. reported to Maplesoft.

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

 > interface(version);

 > Physics:-Version();

 > restart;

 > u:=Int(2/3/alpha^(3/2)*sin(1/2*3^(1/2)*ln(alpha))*sin(alpha)*3^(1/2),alpha = 0 .. x)

 > value(u);

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.

## why dsolve with Lie option gives ones le...

The ode  diff(y(x), x)^3 = y(x)*sin(x) should have 3 solutions since it is cubic in diff(y(x),x) and the each of the 3 generated ode's has one solution.

ode:=diff(y(x), x)^3 = y(x)*sin(x);
sol:=PDEtools:-Solve(ode,diff(y(x),x));
Vector(map(X->dsolve(X,'explicit'),[sol]))

But In Maple 2024, using Lie option gives 2 solutions only, while default dsolve gives 3 solutions.

In Maple 2023 using Lie option gives 6 solutions for some reason.

So something changed in Lie solver for dsolve.

Btw, in all the above I am discarding the extra y=0 solution as this is trivial solution and should not have been returned any way, but this is not a big issue

Basically, Maple 2024 Lie solver gives now 2 non trivial solutions when there should be 3 non trivial solutions.

Any one could give an idea why this happens? Should not both solvers return same number of non trivial solutions?

 > interface(version);

 > Physics:-Version();

 > ode:=diff(y(x), x)^3 = y(x)*sin(x)

 > Vector([dsolve(ode)])

 > Vector([dsolve(ode,useInt,'explicit')])

 > Vector([dsolve(ode,Lie)])

 >

This below is in Maple 2023 showing difference in Lie solutions

 > interface(version);

 > ode:=diff(y(x), x)^3 = y(x)*sin(x)

 > Vector([dsolve(ode)]);

 > Vector([dsolve(ode,Lie)])

 >