Hey there,

I am using the fsolve command in order to solve numerically a system of equations with N equations and N unknowns. According to my discretization the number of equations changes. If I have a small number of equations it all works out perfectly. But if I increase the number of equations I just get something like that:

Sorry, for the long post, but for a small number of unknowns Ai it works. It seems that maple doesnt try to compute? Has anyone encountered the same problems?

Any help is appreciated.

Jens

Greetings to all. The title describes it well, I am writing about testing the limits of the Maple integration engine. A recent discussion at math.stackexchange.com features a family of integrals that involve the product of a power of the natural logarithm and a rational function, more precisely,

int((log(x))^n/(x^3+1), x=0..infinity);

These integrals can be evaluated recursively as described at the MSE link using a technique that generalizes to other types of rational factors. Unfortunately Maple apparently only finds a simple closed form for a few small initial values of n. The following transcript of a Maple session illustrates the problem. Mathematica was successful here. Also observe the memory allocation in the Maple session.

    |\^/|     Maple 18 (X86 64 LINUX)
._|\|   |/|_. Copyright (c) Maplesoft, a division of Waterloo Maple Inc. 2014
 \  MAPLE  /  All rights reserved. Maple is a trademark of
 <____ ____>  Waterloo Maple Inc.
      |       Type ? for help.
> restart; read `cl.maple`;
alpha := (n, k) ->

                                                           n
    -1/3 exp(1/3 I Pi + 2/3 I Pi k) (1/3 I Pi + 2/3 I Pi k)

Q := proc(n)
local res;
option remember;
    if n = 0 then return 2/9*sqrt(3)*Pi end if;
    res := -add(alpha(n + 1, k), k = 0 .. 2)/(n + 1) - add(
        binomial(n + 1, p)*(2*I*Pi)^(n - p)*Q(p),
        p = 0 .. n - 1)/(n + 1);
    simplify(res)
end proc

                               infinity
                              /               n
                             |          log(x)
              VERIF := n ->  |          ------- dx
                             |           3
                            /           x  + 1
                              0

> Q(6);
                                7  1/2
                          910 Pi  3
                          ------------
                              6561

> VERIF(6);
memory used=3.8MB, alloc=40.3MB, time=0.18
       7  1/2
9890 Pi  3       490    5  1/2
------------- + ----- Pi  3    Psi(1, 1/3)
   177147       19683

        490    5  1/2                10    3  1/2            2
     + ----- Pi  3    Psi(1, 2/3) + ---- Pi  3    Psi(1, 1/3)
       19683                        2187

        20   1/2   3
     + ---- 3    Pi  Psi(1, 2/3) Psi(1, 1/3)
       2187

        10    3  1/2            2    40                 4
     + ---- Pi  3    Psi(1, 2/3)  + ----- Psi(2, 2/3) Pi
       2187                         19683

        10   1/2               3
     + ---- 3    Pi Psi(1, 1/3)
       2187

       10               1/2               2
     + --- Psi(1, 2/3) 3    Pi Psi(1, 1/3)
       729

       10   1/2                           2
     + --- 3    Pi Psi(1, 1/3) Psi(1, 2/3)
       729

        10   1/2               3    40     4
     + ---- 3    Pi Psi(1, 2/3)  - ----- Pi  Psi(2, 1/3)
       2187                        19683

        20             2  1/2
     + ---- Psi(2, 2/3)  3    Pi
       6561

        40               1/2
     - ---- Psi(2, 2/3) 3    Psi(2, 1/3) Pi
       6561

        40    2
     + ---- Pi  Psi(2, 2/3) Psi(1, 1/3)
       2187

        40    2
     + ---- Pi  Psi(2, 2/3) Psi(1, 2/3)
       2187

        20   1/2            2
     + ---- 3    Psi(2, 1/3)  Pi
       6561

        40    2
     - ---- Pi  Psi(1, 1/3) Psi(2, 1/3)
       2187

        40    2
     - ---- Pi  Psi(1, 2/3) Psi(2, 1/3)
       2187

> evalf(Q(6));
                          725.5729634

> evalf(VERIF(6));
                          725.5729630

> quit
memory used=22.4MB, alloc=44.3MB, time=0.47
user@host:~/complex-logint$ math
Mathematica 10.0 for Linux x86 (64-bit)
Copyright 1988-2014 Wolfram Research, Inc.

In[1]:= Integrate[Log[z]^6/(1+z^3), {z, 0, Infinity}]

                7
          910 Pi
Out[1]= ------------
        2187 Sqrt[3]

In[2]:= N[Out[1]]

Out[2]= 725.573

In[3]:=
user@host:~/complex-logint$

My question for you all is what the appropriate techniques would be to get Maple to at least simplify the rather involved output from the integration engine to obtain a match of the closed form from the recursive equation.

Best regards, Marko Riedel.

cl-maple.txt

Below z is made using different complex values on polar form, and I then need to express the resulting z on polar form with numeric values for length and angle.  However, I had no luck using evalc, evalf, or other I could find.

How can I convert z to a polar form with numeric arguments like shown below ?

Trying to solve this IVP of the SHO  (second order linear costant-coefficient).

Everything works fine until I come to the solving even after using dsolve with initial conditions (even using the differential operator D in the initial conditions)  , the answer still contains _C1, an unknown constant.

The full worksheet is below.  The code for dsolve is:

sol3 := dsolve(subs(par1, {de1, D(x)*0 = 0, x(0) = 1}), x(t));

Hoping you can help with a solution.

Hi guys.

           if an expression complicated as the following,  

sqrt(sqrt(9)*sqrt((1+(b+1)^2*c^2+((10/3)*b-2)*c)*(1+(b+1)^2*c^2+(2*b-2)*c))+3+(3*b^2+6*b+3)*c^2+(8*b-6)*c) , where b>0 c>0

is it possible to tell whether it could be positive? 

I used coulditbe command, however, it returned 'FAIL'.

Having a function where the value is for example only defined when abs(x) <= 1, then how can I specify that the value is otherwise undefined, the replacing "How_to_specify_undefined_value" below?

It would be nice if the StringTools package had a function giving the number of primitive words of length n on an alphabet of size a.  The formula for this is well-known but tedious to code.

I am using Maple 2015.2 on a Windows 10 machine.  I use the plot command to generate a simple graph.  I then use the Manipulator Pan tool to change the axes limits.  The system does not redraw the function with the new range limits.  The parameters in the Axis properties have been changed appropriately but the graph does not display for the new limits.  Even if I change the parameters without using Manipulator Pan tool, the system does not redraw the function with the new range limits.  Any guidance about what I am doing wrong?  I am attaching an example file in case the behavior continues on other systems.

20160711_example_of_graph_pan_issue.mw

Thanks,

Wayne

Dear All

It is well known that the package "PDEtools" is helpful in finding infinitesimal transformations for PDEs which I illustrate as follow:

Download Writing_Vector_fields.mw

Regards

        General description of the method of solving underdetermined systems of equations. As a particular application of the idea proposed a universal method  kinematic analysis for all kinds of  spatial and planar link mechanisms with any number degrees of freedom.  The method can be used for powerful CAD linkages.   
         http://www.maplesoft.com/applications/view.aspx?SID=154228

       

      Some examples of a much larger number calculated by the proposed method. Examples gathered here not to look for them on the forum and opportunity to demonstrate the method.  Among the examples, I think, there are very complicated.

https://vk.com/doc242471809_408704758
https://vk.com/doc242471809_408704572
https://vk.com/doc242471809_376439263
https://vk.com/doc242471809_402619761
https://vk.com/doc242471809_402610228
https://vk.com/doc242471809_401188803
https://vk.com/doc242471809_400465891
https://vk.com/doc242471809_400711315
https://vk.com/doc242471809_387358164
https://vk.com/doc242471809_380837279
https://vk.com/doc242471809_379935473
https://vk.com/doc242471809_380217387
https://vk.com/doc242471809_363266817
https://vk.com/doc242471809_353980472
https://vk.com/doc242471809_375452868
https://vk.com/doc242471809_353988163 
https://vk.com/doc242471809_353986884 
https://vk.com/doc242471809_353987119
https://vk.com/doc242471809_324249241
https://vk.com/doc242471809_324102889
https://vk.com/doc242471809_322219275
https://vk.com/doc242471809_437298137
https://vk.com/doc242471809_437308238
https://vk.com/doc242471809_437308241
https://vk.com/doc242471809_437308243
https://vk.com/doc242471809_437308245
https://vk.com/doc242471809_437308246
https://vk.com/doc242471809_437401651
https://vk.com/doc242471809_437664558

I am having 26th degree polynomial univariate equation , I used Isolate to get the roots. but I am getting some extra roots which are not true they I even tried to substitute those roots in original equation then I got non zero answer instead of getting nearly zero answer.How is it possible??

equation looks like:

-12116320194738194778134937600000000*t^26+167589596741213731838990745600000000*t^24+1058345691529498270472972795904000000*t^22-4276605572538658673086219419648000000*t^20-23240154739806540070988490473472000000*t^18-5442849111209103187871341215744000000*t^16+49009931453396028716875310432256000000*t^14+74247033158233643322704589225984000000*t^12-2762178990802317464801412907008000000*t^10-25947900993773120244883450232832000000*t^8-7468990043547273070742668836864000000*t^6-567730116675454293925108383744000000*t^4+3703566799705707258760396800000000*t^2-4742330812072533924249600000000

Solutions i got:

[t = -4.162501845, t = -2.295186769, t = -1.300314688, t = -.8048430445, t = -0.6596008501e-1, t = -0.4212510777e-1, t = 0.4212510777e-1, t = 0.6596008501e-1, t = .8048430445, t = 1.300314688, t = 2.295186769, t = 4.162501845]

t=4.162501845 give me non zero answer when I substitute it in the equation given above:

I got this answer: 4.750212083*10^39

Hi there,

            Recently, I encountered a problem. I have a function( omega as its variable)  (18)

 gamma*sqrt(4)*sqrt(omega^2*C2^2*R4^2/(C2^4*R4^4*beta^2*gamma^2*omega^4+C2^2*(1+gamma^2*(beta+1)^2-2*gamma)*R4^2*omega^2+1))

I tried to find a point where its first derivative equals 0. In this case, Maple returned four solutions. In my

question, both beta, gamma, R4 and C2 >0， I want it to return a real positive solution, the first term

in (19) (i.e. 1/(sqrt(beta *gamma) *1/R4 C2).

I know it is easy to find out the positive real roots in this case. This question seems to make no sense.

However, sometime I came across an expression complicated enough that I cannot tell whether it is real

positive.

Is there a approach to find a real positive solution of an symbolic eqution?

Thanks in advance!

                                                                     A University student in BeiHang University, Beijing

I'm trying to call a C function which returns an array. The example on the help page http://www.maplesoft.com/support/help/maple/view.aspx?path=examples/ExternalCalling is to pass in an array with known dimensions, which will be updated in the C function, but I wonder if this is the only way to do it. For example if I have an array of unknown dimensions beforehand, what is the best approach to return this array?

Thanks!

I am trying to solve a matrix system to find the relative arrival rates of a queueing network using Gauss-Seidel.The maple commands are below:

restart;
with(Student[NumericalAnalysis]); with(LinearAlgebra);

A := Matrix([[1, -.333, -.333, -.333], [0, 1, -.333, -.333], [0, -.333, 1, -.333], [0, -.333, -.333, 1]]);

IsDefinite(A, 'query' = 'positive_semidefinite');

true

b := Vector([1, 1, 1, 1]);

IterativeApproximate(A, initialapprox = Vector([1, 1, 1, 1]), tolerance = 10^(-3), maxiterations = 20, stoppingcriterion = relative(infinity), method = gaussseidel);

Error, (in Student:-NumericalAnalysis:-IterativeApproximate) check that the augmented matrix has the correct dimensions

I do not understand this error as the matrix is 4x4 as shown. Can anyone see where I went wrong?

 Hello every one,how do i integrate from this expression?

Download integral.mw