## why the the software can't solve the integral like...

why the the software can't solve the integral like ∫xdlnx？

## Get Error in "DGsetup([t, r, theta, phi], M1, verb...

Hi, I am learning GR and new to maple. I played with maple's DifferentialGeometry package.

While duplicated the maple GR example, in DGsetup([t, r, theta, phi], M1, verbose),

I got the error,

DGsetup([t, r, theta, phi], M1, verbose)

The following coordinates have been protected:
[t, r, theta, phi]

The following vector fields have been defined and protected:

Error, (in Typeset:-Tdisplay[true]) `alias` does not evaluate to a module

I don't know how to fix it. Can anyone kindly help?

Thanks

## Solving system of equations...

Hi, I have 10 equation system and 10 unknown variables. I however, want to reduce the equations to 2 with two unknowns. I'm wondering how this could be done in maple. The variables are Y, q, yd, y*, yx, H,  pd, w, P and Pv. I intend to solve the equations for Y and w.

Thanks in advance for your help. The maple file has also been attached.

Regards

Small_Open_Economy.mw

## Error, (in dsolve/numeric/bvp/convertsys) unable t...

thanks a lots.....

dsys3 := {8*(diff(f2(x), x, x, x, x))+9*(diff(f2(x), x, x))+10*f2(x)+11*(diff(f1(x), x, x, x))+12*(diff(f1(x), x))+13*(diff(f3(x), x, x))+14*f3(x)+f3(x)*f3(x)+(diff(f3(x), x))*(diff(f3(x), x))+(diff(f3(x), x, x))*f3(x) = 0, 16*(diff(f3(x), x, x, x, x))+18*(diff(f3(x), x, x))+19*(diff(f3(x), x, x))+22*(diff(f1(x), x))+23*(diff(f1(x), x))+24*(diff(f2(x), x, x))+25*f2(x)+26*f2(x)+27*f3(x)+29*f3(x) = 0, 2*(diff(f1(x), x, x))+3*(diff(f2(x), x, x, x))+4*(diff(f2(x), x))+6*(diff(f3(x), x))+7*f1(x)+(diff(f3(x), x, x))*(diff(f3(x), x))+(diff(f3(x), x))*f3(x)+(diff(f3(x), x))*f3(x) = 0, f1(0) = 0, f1(1) = 0, f2(0) = 0, f2(1) = 0, f3(0) = 0, f3(1) = 0, ((D@@1)(f2))(0) = 0, ((D@@1)(f2))(1) = 0, ((D@@1)(f3))(0) = 0, ((D@@1)(f3))(1) = 0}; dsol5 := dsolve(dsys3, 'maxmesh' = 500, abserr = .1, numeric, range = 0 .. 1, output = listprocedure)12.mw

## How to determine unknown value in boundary conditi...

Hello everyone,

How can unknown values in boundary conditions of system ODEs be determine by using shooting technique. See the work sheet here Sht.mw

Thanks.

## plot3d problems...

Hi,

I am experiencing some problems with the plot3d command. It does not return a nice 3d-graph, but just a bunch of dashed lines. I have entered something like this:

with(plots):

plot3d(x*y,x=-1..1,y=-1..1);

I am using maple 17 on windows 7

## How can PDE be solved in terms of Bessel function?...

Good day everyone,

please how can one solve this pde in terms of Bessel function or any other analytic solution with the plot.

See the file ID.mw

Thanks.

## how to using maple code convert to mathematica cod...

Does anyone know how to using some softward convert ?  for example  I have maple code , but I want to using mathematica code .I need fast way.

## particular solution of ODEs in Maple...

Могу ли я использовать Клен, чтобы найти конкретные решения, которые выражаются либо в начальных и эллиптических функций для систем обыкновенных дифференциальных уравнений. Например, вы можете получить в Maple решений (sub_Solve01, sub_Solve02) для систем, которые перечислены в файле?
exp01.mw

## difficult integral that Maple cannot solve it...

integral.mw

Hi all, I want the best for you.

I really have confused with this bad integral (HeunB)which I've got it 2 weeks ago from a solution by Maple 17. I should solve this one to solve the derivative of this too.

Help me please, I attached the attribute file.

Regards.

## Problem in evaluating function to numeric values i...

Hi, I'm a big noob in Maple, so may be the answer is very simple.

Thank you!!! ## How can linearization be done with maple...

How can one use maple to linearized nonlinear ODE of this type Linearize.mw

with maple.

Best regards.

## Solving a piecewise differential equation system...

Hi there,

I've got the following differential equation system:,

dU/dt = delta·dotD -lambda·U - kappa·U^2
dL/dt = (1-phi)·lambda·U + 1/4 ·kappa·U^2

being phi, delta, kappa, lambda, kappa some fixed parameters of the system, and where dotD (the derivative wrt time of a function D), which is defined a piecewise funtion:

dotD(t)=1/(3·T1)·DT for t in [0,T1]

dotD(t)=2/(3·(T2-T1-T))·DT for t in [T1+T,T2]

where T and DT are also known, and T1 approaches 0, and T2 approaches T1+T.

Setting the equation system in Maple and trying to solve it, gives a NULL result. However, trying to solve each piece separately seems to work fine.

Why is this?

Furthermore, taking limits for the [T1+T,T2] part (having solved each piece separately) yields an invalid limits point error. Ain't the possibility to take limits for both parameters at the same time?

Any ideas?

This is the Maple worksheet: MaplePrimes_LQ_model_solve.mw

Thank you.

jon

## Maximizing a function...

Hi there,

I am trying to maximize a function given a set of values to a parameter in the function. The function is an differential equation belonging to a system of two differential equations.

I have a for loop to state different values to the parameter.

Maple yields the error:

Error, (in Optimization:-NLPSolve) cannot evaluate the solution further right of 0.17757507e-4, probably a singularity

When trying to maximize the function.

Supposed that I was doing something wrong in the loop, if I reproduce the contents of the loop outside, and set a value for the parameter. If I plot the solution of the ordinary differential equation, I can see where the maximum lies.

Having plot it, the Optimizamtion:-Maximize works as expected.

However, omitting the plot has a weird effect: I only get the same result depending on the bounds I set for the Maximization:

de1 := diff(A(t), t) = r*m*(1-g)*A(t)-piecewise(t < 8, r*A(t), t >= 8, (r+k)*A(t));
de2 := diff(G(t), t) = r*m*g*A(t)-l*G(t);

ics := A(0) = 25.0, G(0) = 0.;
num := dsolve({de1, de2, ics}, {A(t), G(t)}, type = numeric, output = listprocedure, parameters = [g]);

num(parameters = [g = .15]);
val := eval(G(t), num);

# odeplot(val, [t, G(t)], t = 0 .. 100);

Maximize(val);
Error, (in Optimization:-NLPSolve) cannot evaluate the solution further right of 0.17757507e-4, probably a singularity

val2 := Maximize(val);

Error, (in Optimization:-NLPSolve) cannot evaluate the solution further right of 0.17757507e-4, probably a singularity

val3 := Maximize(val(t), t = 0 .. 60);

[10267.824035766165, [t = 8.25727747134303]]

val4 := Maximize(val(t), t = 0 .. 100);

[6.863211343195069e-9, [t = 59.84184367042171]]

The right answer is [10267.824035766165, [t = 8.25727747134303]]: Why do I get two different answers even if in that range there is only one relative maximum?

I ignore whether the way I am specifying the arguments for the Maximize function is correct. val is a procedure.

What am I missing?

Attached is the worksheet: MaplePrimes_malaria_param_variation_2.mw

Thanks,

jon