## Maple hangs when computer is locked during workshe...

If worksheet execution was started and computer is locked before execution ends, Maple will stop responding and all work is lost. Execution of whole worksheet takes very long time, sometimes over 3 hours, so "do not lock computer during execution" is not solving the problem.

## Combine two solutions from LPSolve and take the va...

Dear All,
Perhaps my question is basic question, but I want to know more about LPSolve
Is it possible to join 2 solutions from different LPSolve?

For example, I have 2 solutions,
Sol[1] := [72.011122301, [t[4] = -.500000000000000, t[13] = .500000000000000, x[1, 4] = 1, x[1, 13] = 0, x[4, 1] = 0, x[4, 13] = 1, x[13, 1] = 1, x[13, 4] = 0]];
Sol[2] := [53.128387340, [t[6] = -2.00000000000000, t[7] = 0., t[8] = -.999999999999999, x[1, 6] = 1, x[1, 7] = 0, x[1, 8] = 0, x[6, 1] = 0, x[6, 7] = 0, x[6, 8] = 1, x[7, 1] = 1, x[7, 6] = 0, x[7, 8] = 0, x[8, 1] = 0, x[8, 6] = 0, x[8, 7] = 1]].

What I want to achieve is following:

(1) eliminating t variable and join those solution (all values of x). Thus, I got [ x[1, 4] = 1, x[1, 13] = 0, x[4, 1] = 0, x[4, 13] = 1, x[13, 1] = 1, x[13, 4] = 0,x[1, 6] = 1, x[1, 7] = 0, x[1, 8] = 0, x[6, 1] = 0, x[6, 7] = 0, x[6, 8] = 1, x[7, 1] = 1, x[7, 6] = 0, x[7, 8] = 0, x[8, 1] = 0, x[8, 6] = 0, x[8, 7] = 1]].
(2) Extracting the value of X. I know that sol[1][2] indicates the values of right hand side. But I want to get the value of each of x in sequence.
for example: I can get x[1,2]=1, x[1,8]=0, x[7,1]=0 and so on.
In this case, Maybe I can use
eval(x[1,8],sol[1]) for specific x.
But is there any nice way to get all values of x with some procedures?

## efficient coding for procedure...

What are the most efficient way to write and evaluate a procedure in maple? Thank you.

## Elliptical Pde solution...

Dear sir,

I am using the Maple to solve pde equations but I am not getting analytical solutions for some of the equations. Can you please help me on how to solve one of the pde, like as I have

(sin(theta)^2*(diff(a(r, theta), r, r))+cos(theta)^2*(diff(a(r, theta), r))/r-sin(2*theta)*(diff(a(r, theta), theta))/r^2+sin(2*theta)*(diff(a(r, theta), theta, r))/r+cos(theta)^2*(diff(a(r, theta), theta, theta))/r^2)*`&alpha;__d`^2+cos(theta)^2*(diff(a(r, theta), r, r))+sin(theta)^2*(diff(a(r, theta), r))/r+sin(2*theta)*(diff(a(r, theta), theta))/r^2-sin(2*theta)*(diff(a(r, theta), theta, r))/r+sin(theta)^2*(diff(a(r, theta), theta, theta))/r^2 = 0

this equation is in polar corrdinates, this is analogous to diff(a(x, y), x, x)+`&alpha;__d`^2*(diff(a(x, y), y, y)) = 0

in cartesian coordinates

## How to improve these procedures ?...

Duo:=proc(a)  #a nombre congruent connu
local u,v,n,m,k,t:
t:=8000:
for m to t do
for n to m do
if (igcd(m,n)=1 and m>n) then
u:=(m^2-n^2-2*m*n)^2:v:=(m^2+n^2)^2:
k:=op(2,sqrt(v-u))^2: # k nombre congruent réduit
if k=a then return (m,n): break
elif n=t then break fi:
fi:
od:
od:
end:

Duo(30);
3, 2
Duo(1794);
26, 23
Duo(6);
2, 1
u, v, w sont des carrés en progression arithmétique dont la raison est un nombre congruent
Procédure permettant de trouver un triplet pythagoricien primitif correspondant au nombre congruent a connu
TriPy:=proc(m,n)# triangles pythagoriciens
local a,a1,b1,c1,d,k,q,u,v,w:
if (igcd(m,n)=1 and m>n) then
u:=(m^2-n^2-2*m*n)^2:v:=(m^2+n^2)^2:w:=(m^2-n^2+2*m*n)^2:
a:=(op(2,sqrt(v-u)))^2:#nombre congruent réduit
a1:=2*m*n:b1:=(m^2-n^2):c1:=m^2+n^2:
q:=sqrt((v-u)/a)/2:#rapport de réduction
print(a1/q,b1/q,c1/q):fi
end:
TriPy(Duo(34));
17  145
24, --, ---
6    6

TriPy(Duo(39));
156  5  313
---, -, ---
5   2  10

TriPy(Duo(111));
444  35  1513
---, --, ----
35   2    70
TriPy(Duo(1794));
1196      1205
----, 21, ----
7         7
TriPy(Duo(23));don't work, "part dans les choux"

## How to take derivative of a function with summatio...

Hi, how can you in maple take the derivitve of a function that consists of sum terms in it? (preferable in document mode)

For example I have this expression (from a math book):

f = N+k*(sum(ln(x__i-B), i = 1 .. N))-N*k*(sum((x__i-B)^k*ln(x__i-B), i = 1 .. N))/(sum((x__i-B)^k, i = 1 .. N))

What I then want to do is to derive this function with respect to k.
However just writing the expression like above it seems like mable doesn't keep the summation terms but evaluates them in a sense. So not sure how to set it up correctly in order to make the derivitive.

Taking the derivitive of f with respect to k, the solution should give something like this:

## simplify equations...

How  I can use from equations 1-6 and repleacing them into equation 7 to remove qx,qy,qz?

Thank you

 >
 (1)
 >
 (2)

 >
 (3)
 >
 (4)

 >
 (5)
 >
 (6)

 >
 (7)

## How can plot option color display a rolling wheel?...

with(plots);
for x to 10 do Disp[x] := plot([x+cos(a), sin(a), a = 0 .. 2*Pi], colorscheme = ["Red", "Green"]) end do;

display(seq(Disp[i], i = 1 .. x-1), insequence = true, scaling = constrained);

What coding in the color or colorscheme parameter in the plot command above would rotate the circle's colors in conjunction with the circle's movement along the x axis to give the appearance of a rolling wheel?

## running job in windows comand line...

I am submitting a maple job written in vim editor through windows 10 command line. but no result is obtained.I found maple gui version hang most of the time. So i decided to submit through command line by writing codes using an editor. Thank you

## im trying to plot a function involving "e" but kee...

I'm trying to plot a function involving exp but keep getting warnings.

How can i avoid this?

plot(2*cos(t)/sqrt((1+exp(-eps*t))*(4/a^2-1)))

but getting the warning message

"Warning, unable to evaluate the function to numeric values in the region; complex values were detected"

## Symbolic x and y in an equation - How do I retain...

I have made a document to give the results for a problem in table form and graph form.

The tables work out well. The graph results also come out well when I have that section alone in the document. But it does not give the updated curve here. Please correct me where I made mistake.

 Cost in \$: Present Value: Interest in % per year: Period in years: Additional Months

 Principal \$ Interest % per year Year Present value at the year end

UpdateExpr procedure does not update equation, instead turns out a value on LHS

 Cost: Interest % per year (float)

Startup Code Region contains all the codes.

Thanks.

## How to use Euler’s method with a step size of Δt=...

​​​​

RC-Circuit:         (dv_c)/dt=((V(t)-v_c ))/RC

Assume thatV(t)=2 cos⁡(3t),R=4 ,C=0.5 . Use Euler’s method with a step size ofΔt=0.1to approximate the solution of IVP with initial conditionv_c (0)=2over the interval0≤t≤10 .

## How to use Maple to plot the approximate solution...

I can't find anything online on how to use Maple to solve this question, I have attempted it but want to make sure I did it correctly.

Use Maple to plot the approximate solution, the slope field, and (if possible) the exact solution on the same axes. Also compute the error between the approximate solution obtained from Euler’s Method and the exact solution at the right end-point of the given interval.

1.      dy/dt=(3-y)(y+1)   ,   y(0)=4 ,        0≤t≤5 ,        Δt=1.0

## How do I extract a matrix from an LPSolve solution...

LP_Matrix.pdf

Hello!

I'm missing something basic here, I'm sure, and would love to know how to proceed.

I have extracted solutions to a particular optimization problem using LPSolve and have obtained the binary solutions in matrix form, for matrices, say .. X and Y.

The solutions are obtained using the routine in the attached pdf; these outputs are sufficient for the basic problem.

Now, I wish to use directed graphs to illustrate the solutions, so I need to take the output matrices to draw the graphs. However, I cannot seem to find a way to do this. The solutions are given, in this case, by 'X' and 'Y'.

Can anyone advise me on how to extract the matrices that can be used to draw the graphs using with(Graph Theory)?

## Big MapleSim model can't be totaly simplified...

Hello,

I use MapleSim to model the dynamics of motorcycles.
I have been at MapleSim2018 for a few months and I have a problem of simplifying the equations generated by MapleSim from my model.

Processing Equations...
SelectCompiler: Check for installed compiler successful
Simplifying system with 8919 equations
DSN/ix1lite: Warning, equation size increased past 100000 while performing equation simplification. Model will be simulated in partially unsimplified form
Simplification removed 8428 equations. Remaining equations: 491
Generating simulation code

the same model (exactly the same) in MapleSim2016, he tells me :

Processing Equations...
Simplifying system with 8942 equations
Simplification removed 8494 equations. Remaining equations: 448
Generating simulation code

When I generate code from two versions of Maple (2016 and 2018) and compile it into an executable, the MapleSim 2018 executable runs 20% slower than the MapleSim 2016 version of the executable (the results and the behavior of both models are equivalent)

It is very strange that a new version of MapleSim generates a slower code than the old version. it may be due to the limitation of DSN / ix1lite in MapleSim2018 ... while MapleSim2016 does not have this limitation (with more equations to simplify!).

I need help, if it is possible to activate the complete simplification in DSN / ix1lite?

it is a big problem for me, the use of MapleSim2018 is not possible because of that. My model does not pass in real time.

thanks.

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