## How to solve BVP with singularities?...

Dear friends,

I have to solve the BVP of the following type:

(x-1)*y''(x)+y'(x)=1+x, y(0)=1, y(1)=1

Expressing the highest derivative (y''(x)), we get a singularity at x=1.

So, as recommended, the method bvp[middefer] (or bvp[midrich]) is used:

`dsolve({(x-1)*diff(y(x), x\$2)+diff(y(x),x) = 1+x, y(0)=0, y(1)=1}, type = numeric, method = bvp[middefer], y(x), 'output' = Array([seq(k/10, k=0..10)]), 'abserr'=1.0e-3, 'maxmesh'=100)`

Maple generates the following error:

Error, (in dsolve/numeric/bvp) unable to achieve requested accuracy of 0.10e-2 with maximum 100 point mesh (was able to get 0.82e3), consider increasing `maxmesh` or using larger `abserr`
But as I increase maxmesh, the achievable accuracy (reported in "(was able to get XXX)") decreases:

for

maxmesh = 200: 0.19e4

maxmesh = 500: 0.54e4

maxmesh = 1000: 0.12e5

maxmesh = 5000: 0.73e5

and so on.....

How to solve this equation with desirable accurancy and usage of Array as output?

## intial value is not converging...

Dear please check once it showing an error program.mw as intial value is not conververging

## Need convergent solution...

Dear, I am facing the problem for solvin the attached file. Solution obtained for L=1 successfully but i need the solution for large value of L e.g., L =10. Please find the attachement and fix the problem. I am waiting positive response. Thanks in advance.

Help.mw

## Plotting the movement of 4 planets...

Greetings,

currently im working on a project in which i basically have to calcuate and plot a little solar system, using newton mechanic. The work is done, but as it appears, the solution simply cannot be true. In the given example you can see that the planets move in more or less straight lines. I presume that the error is somewhere in the solution of the system of differential equations, but i can't see where it is.

I am grateful for every advice.

PlanetenSpacecurve.mw

## command to retrieve a solution...

Hi

I have a set of differential equations which I have solved for a specific value, and would like to use the second answer (F__A(V)) in my next calculations

What command can I use to retrieve that value?

sol(0.1e-4);
[V = 0.00001, F__A(V) = HFloat(3.498873118476744e-6),

F__B(V) = HFloat(1.9101126881523255e-5),

F__C(V) = HFloat(9.550563440761627e-6)]

Regards

## Use of numerical solution...

Hi, similar problem as before :) I want to use numeric solution DE while solving another DE. Example:

sol:=dsolve(Dsys,numeric)

dsolve({diff(y(x),x)=y(x)-sol,y(0)=1},numeric)

The second part doesn´t work. Can you help me to fix it? Thank you :)

## Finding the eigenvalues...

Hello guys,

I have some system of differential equations,

How can i find  eigenvalues of this system?

`If i have solution`

res := evalf(dsolve(sys union ics, convert(x, list), type = numeric, method = rkf45))

and

sol := evalf(dsolve(sys union ics, convert(x, list), method = laplace))

AnSolution.mw

Thanks!

## Numeric problem...

Hi,

I want to subtract two functions. One of them is numeric-type and the second is exact. Something like this:

solNum := dsolve(Dsys, numeric);

sol := dsolve(Dsys);

plot(solNum-sol)

In the last step there is an error (of course). How can I fix it?

Thank you very much

## Boundary value problem...

(1)How can i draw a graph by considering eta on x-axis and f'(eta),theta(eta)on y-axis in a single graph with respect to variatiation  in the parameter beta=0.01,0.1,1.0..

(2). how can i get different values of f'(eta) by varying values of eta .

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## My system of equation was ODE, but Maple insists i...

I was trying to solve a system of ODE using Maple, but to my surprise, Maple recognizes diff((phi(t), t)) as a variable which is different than t.

My code is as following:

dsys := {2*m1*(a+l*sin(phi(t)))^2*(diff(diff(theta(t), t), t))+4*m1*(a+l*sin(phi(t)))*l*cos(phi(t))*(diff(theta(t), t))*(diff(phi(t), t)) = M, 2*m1*l^2*(diff(diff(phi(t), t), t))+4*m2*l^2*sin(2*phi(t))*(diff(phi(t), t))*(diff(phi(t), t))+4*m2*l^2*sin(phi(t))^2*(diff(diff(phi(t), t), t))-2*m1*(a+l*sin(phi(t)))*l*cos(phi(t))*(diff(theta(t), t))*(diff(theta(t), t))-2*m2*l^2*(sin(2*phi(t)))(diff(phi(t), t))*(diff(phi(t), t)) = -(2*(m1+m2))*g*l*sin(phi(t))-2*k*l^2*sin(2*phi(t)), phi(0) = 0, theta(0) = 0, (D(phi))(0) = 0, (D(theta))(0) = 0}

subs({M = 10, a = .5, g = 9.81, k = .1, l = .5, m1 = 10, m2 = 1}, dsys);

dsn1 := dsolve(dsys, numeric)

The error I got was Error, (in dsolve/numeric/process_input) input system must be an ODE system, got independent variables {t, diff(phi(t), t)}

I don't get why this is happening. Could you show me what's going on?

## How to create a data table from dsolve?...

I have a system of ode's

restart:with(plots):
eq1:=((diff(f(x),x\$3)))+f(x)*diff(f(x),x\$2)-a*diff(f(x),x\$1)^2=0;
eq2:=(diff(g(x),x\$2))+b*f(x)*diff(g(x),x\$1)=0;
bc1:=f(0)=0,D(f)(0)=1,D(f)(5)=0,g(0)=0.5,g(5)=0;

dsolve can solve it easily.

sol:=dsolve(subs(a=0.5,b=0.5,{bc1,eq1,eq2}), numeric):

Now I was to use the numerical data from the sol in the following expression

Expr:=a*f(x)+b*g'(x)+c*f'(x)*g(x) # at x=1:

to make a table of this form a  b  c  Expr, where a, b, c vary simultaneously between 0 and 1 by 0.2 producing data for Expr.

Any suggestions?

## what happen with this numerical differentiation of...

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when i try to get a numerical solution(using fdiff) for a second order derivative from a numerical diff ecuation procedure i got "index out of range". however, it perfectly works with a first order derivative. what's thwe matter there?

thankyou very much..

## How to improve the numerical solution of BVP (FDM ...

I have solved a BVP using finite difference method in maple. But the comparsion with the dsolve solution shows big difference,

Why there is too much difference? Is there an elegant way to implement FDM?

FDM_Dbvp_sheet_1.mw

## Error in dsolve/numeric/bvp...

Hello every one ;

i have these flowing error :

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any solution ?

thank you

Best regards !

## why is this DAE system crashing?...

could you help with this? maybe because of too long exponents or just a maple bug?

when i try to solve this DAE it just crash. it says connection with kernel has been lost, and tells me to look for online help.

thank you very much...