## Error in the calculation of the arc length of a hy...

Good day!

As part of an exercise I've calculated the length of a hypotrochoid numerically. To check my result I repeated the calculation in Maple, but received a different result. When double checking using WolframAlpha I got the same result as with my numerics. Maybe someone of you can tell me where I made a mistake.

Sören

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## how i can remove error ["unable to store %1 when d...

mar.mw
hi..how i can dsolve these differential equations? omega is unknown and fir solving i add an extra boundary condition, but the error "unable to store %1 when datatype=%2" is appear!!!

how i can remove this error?

thanks

## Combinations of the contents of the partitions...

Hello again. 3 questions today, a record for me.

I'm looking for a procedure to do this

Combinatorial_explosion.mw

thankyou.

## Minimum of a list which excludes zero...

Salutations.

for L:=[5,0,10,3]

What command do I require to find minimum of L which excludes 0? [ 3]

FindMinimalElement?

Hi all....

Thanks

## How to use Select...

Experts.

In view of the worksheet:

VRP_permute.mw

What I need is
a) a better way to display the Tour_Distances (from 1 to M) and
b) a way to select tour elements where each component is <= to a specified distance (say <=H) and the corresponding tour(s) (from Tour2).

## How to solve Laplace transformations of systems of...

My question is: Use the laplace transform to solve the system.

dx/dt + d^2y/dt^2 = 5e^(2t)

dx/dt - x - dy/dt + y = 8e^(2t)

x(0) = 2, y(0) = 1, y'(0) = 1

What I've done in Maple:

with(inttrans);
with(DEtools);
eq5 := (diff(x(t), t)+diff(y(t), t\$2) = 5*exp(2*t), t, s);

eq5s := laplace(%, t, s);

eq6 := (diff(x(t), t)-x-(diff(y(t), t))+y = 8*exp(2*t), t, s);

eq6s := laplace(%, t, s);

solve({eq5s, eq6s}, {laplace(x(t), t, s), laplace(y(t), t, s)});

subs({x(0) = 2, y(0) = 1, (D(y))(0) = 1}, %);

eq3 := invlaplace(%, s, t);

How do I simplify?  If you plug it into maple I come up with an answer that has x and y on each side.  I guess I'm just wondering how I can set them equal to each other to solve and get rid of the variable x and y.  I know answer is correct as I've also ran it through ODEtest.  Please help.

However you figure out getting rid of the variables I assume will help me also in solving the next problem:

Use the Laplace Transform to solve the system

dx/dt = 7x - y + 6z

dy/dt = -10x + 4y - 12z

dz/dt = -2x + y - z

x(0) = 5, y(0) = 7, z(0) = 2

I have attempted the second problem much like the first.  Thank you for your time.

## Append number to a list...

Experts,

This may sound like a dumb question, but i'm seeking a procedure to do it better.

with(combinat, setpartition) :
P := [\$2..5] :

Tours := setpartition(P);M:=nops(Tours)

 (1)

number of elements in each 'group'

seq(nops(Tours[i]),i=1..nops(Tours))

 (2)

i need to add 1 to each 'subgroup' : These are the first two:

[[[1,op(Tours[1,1])],[1,op(Tours[1,2])]],[[1,op(Tours[2,1])],[1,op(Tours[2,2])],[1,op(Tours[2,3])]]]

 (3)

I need to add 1 to each 'subgroup' in a more automatic way.

## Partial differential equation...

hi
I want to solve a pde equation:

```equa1 := diff(u(x,y), x, x)-y(1+x) = 0;

# with codition:

con:=u(0,y) = 0, (D(u[x]))(0,y) = 0;
```

the anwer must be :    u(x,y)= y(x2/2  + x3/6)
How can i solve that with maple?

thanks

## pointplot question on adding colour...

I am plotting a pair of lists of points using

pointplot(Listap, Listbp, symbol = point, symbolsize = 1, size = [1200, 1200])

How could is do this with plot so I can add colours? Along the lines Listap(i)^2+Listbp(i)^2 =R, R is in the range 0..1,then colour =R*256 or any other imaginative way of adding colour.

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## Error in numerical solution of nonlinear ode...

i tried to solve a nonlinear ode with numerical method but maple can't solve it and this error occur:

Error, (in dsolve/numeric/bvp) initial Newton iteration is not converging

my maple codes are attached below:

numeriacal_sol.mw

can any help me?

## Can I set limit on number of cores Maple uses ?...

As I understand it, Maple will detect and use the available cores in a system, if the calculation is suitable for multi-core use.

As I am installing Maple on a multi-user cluster, using a scheduler to run maple scripts, I want to ensure the maple jobs only use the number of cores allocated to the job.

Is it possible to set the number of cores used ?

If I have misunderstood how Maple works (I am new to it), or if there is a section in the documentation which explains this, please point me in the right direction.  I haven't found this info so far.

## why simplify command doesn't work for Ei function?...

if I use the command below, I will get the right answer.

`assuming`([simplify((2*I)*deltas*Pi*BW*Ei(1, (2*I)*deltas*Pi*BW)-(2*I)*deltas*Pi*BW*Ei(1, -(2*I)*deltas*Pi*BW))], [real, BW > 0, deltas > 0, ts > 0, deltas <= ts, 2*BW*ts >= 1])

2*BW*Pi*deltas*(Pi-2*Si(2*BW*Pi*deltas))

while I use the same command for the compliacated Ei function, it doesn't work any more, I don't know the reason.

`assuming`([simplify(Ei(1, I*BW*Pi*deltas-(5*I)*BW*Pi*ts)-Ei(1, -I*BW*Pi*deltas+(5*I)*BW*Pi*ts), Ei)], [real, BW > 0, deltas > 0, ts > 0, deltas <= ts, 2*BW*ts >= 1])

and it's reault is :

Ei(1,I*BW*Pi*deltas-5*I*BW*Pi*ts)-Ei(1,-I*BW*Pi*deltas+5*I*BW*Pi*ts)

## Using the Explore command to produce more advanced...

Dear Maple users

I was using the animation command to create an animation consisting of a running sine curve with a ball following the curve, as shown below. I wonder if it is possible to create it with the Explore command too? Or is this command more limited? I need to be able to add more animations, like I can with the display command ...

Regards, Erik.

## Can I solve an inequality with an assumption?...

Hello people in mapleprimes,

I want to modify the inequality of e assuming d.
But, e/(1-a) assuming(d) does not work well.
How can I do for this?

```d:=(a>0,a<1,b>0,c>0);
0 < a, a < 1, 0 < b, 0 < c
e:=(1-a)*b>c;
c < (1 - a) b
e/(1-a)assuming(d);
`*`(c<(1-a)b,1/(1-a))
```