## Workbook mode, variables...

I hope you can help me. I like to use the Workbook feature in Maple 2018. I save variables in one document to use them in another document as well. If, however, the value of the variable changes, I have to delete the variable in the variable manager each time and save it again.
Is there a command I can use to delete and re-save the saved variables?

## Why is Maple registering &t as a neutral operator ...

Hey,

I have just started using Maple for my university project and I am follwing this guide https://www.maplesoft.com/support/help/maple/view.aspx?path=DifferentialGeometry%2FTensor%2FKillingVectors to calculate Killing Vectors. My issue is that when I try and define a metric using evalDG, I need to write dx&tdx to mean the tensor product between the two. Maple interperates this as a neutral operator and gives me "Error, invalid neutral operator".

I am not sure where the issue is as I have written exactly the same code as the guide and yet it gives me an error 3 lines in. Is there some issue that I am not aware of as someone who hasn't used Maple before? Any advice would be useful as I am not really sure how it is possible and I need to be able to write the tensor product to define the metric.

Even for the simplest metric it does not work. My code is:

with(DifferentialGeometry): with(Tensor): with(LieAlgebras):
DGsetup([x, y], M):
g1:=evalDG( dx&tdx):

Any help would be greatly appreciated.

## how I can find solutions for non linear equations ...

how I can find solutions for non linear equations.

I want to find non zero solution.

thank you

ZAH.mw

Maple Worksheet - Error

Failed to load the worksheet /maplenet/convert/ZAH.mw .

## Error, invalid input: unknown uses a 1st argument,...

Hi, Maple is totally new to me and I found something confusing.

Here is what I have:

the_first_element:= proc( A:: Array( numeric ) ) ;
A[1];
end proc():

And it shows Error, invalid input: unknown uses a 1st argument, A (of type Array(numeric)), which is missing.

But in another similar procedure, I have exactly the same lines but it goes without error.

locate_max := proc( A :: Array( numeric ) )
if ArrayNumDims(A) <> 1 then
error "can only search 1d arrays"
end if:
end proc:

I have no idea what is wrong with these 4 lines.

## MapleCloud: The account type or email address or p...

I am on a Mac and unable to login to MapleCloud. I can log in perfectly fine via the website in all browsers. Any solutions for this?

How to simplify

a*b=a*c

to b=c ?

## why is a procedure changing the input?...

I have a procedure that changes the value of an input variable quite unexpectdly. Can anyone explain why? I have a very simplified example of this below.

restart;
with(LinearAlgebra):
switch := proc (V::Vector)
description "This procedure is supposed to take a Vector V and switch entries 1 and 2";
local W,a,b;
W:= V;
a:= W[1];
b:= W[2];
W[1 ] := b;
W[2] :=a;
W
end proc;

V1:=Vector([1,3,5]);
V2:=switch(V1);
I have omitted the output for brevity's sake but all works well as expected.
However,
V1;

returns V2 not V1. Why is the procedure changing V1?

The problem occurs with matrices but not with lists.

Thanks.

## How do i find a solution to a f non-linear equatio...

Hello there,

for academic purposes I need to solve a pretty complex and substantial non-linear equation system. Here you can have a look at the equations:

kompletter_nachbau_v0.mw

The MAPLE Statement "fsolve" is not working here, though there is no error message. I know, that I can provide a framework for each variable to help fsolve find a solution. But for my usage this is not an appropriate task, since I'd like to do some simulations and variations with the input parameters.

Is there a way, so I can find a solution to my equation system?

It would be possible to make some adjustments to my equations, e.g. reducing the complexity of the equations and increasing the number of equations at the same time, if needed.

## How to produce animation in Threads?...

In the worksheet below I produce a sequence of frames for an animation by distributing the task into several threads.  The result has strange artifacts as we see in the sample.  The artifacts vary randomly from run to run.  Am I doing something wrong?

 > restart;
 > kernelopts(version);

 > kernelopts(numcpus);

Draw a simple picture:

 > frame := proc(t)   plot(x^2 + t, x=-1..1, title=typeset("t = %1", t)); end proc:

Generate a sequence of pictures:

 > frames := Threads:-Seq(frame(t), t=0..1, 0.05):

Animate the sequence:

 > plots:-display([frames], insequence);

## How to calculate standard error in nonlinear fit p...

Hi all,

I have a data set (see .txt file attached) to be fit to the model function A*sin(B*x+C)+D. Calculating the parameters A, B, C, and D is easy enough, but is there a way to have Maple return their standard errors?

Data.txt

## Problem with GridPlot command...

Hi,

I can’t perform the last command (GridPlot) on my worksheet

## How do I solve an propositions such as this (exist...

How would I go about getting true or false returned on these propositions?
I have tried just about every eval and various syntax methods, but nothing has worked so far.

I know most can easilly be done by hand/thinking, but I'm sure Maple should have a way to do this as well.

∀n∈Z:2n>n+2   ,   ∃n∈Z:2|(3n+1)    ,   ∃k∈Z:∀n∈Z:n=kn   ,   ∃k∈Z:∀n∈Z:2|(n+k)   ,   ∀n∈Z:∀k∈Z:(n>k∨k≥n)

## help me to solve the eqution by ritz methode codes...

how i can solve the eqution by ritz methode codes?

## problem with verify and trig...

verify(2*cos(phi)^2-1, cos(2*phi), equal); returns FAIL even though is a trig identify. Any ideas why?

## will Maple be able to integrate sin(x)^n,cos(x)^n,...

Maple currently can't integrate things like sin(x)^n or cos(x)^n. These have antiderivative in terms of  hypergeometric functions.

Is there a technical reason why Maple at version 18 still can't integrate these? Will it be able to in next version?

```int(cos(x)^k, x)
int(sin(x)^k, x) ```

fyi, These are the antiderivatives

Same problem for tan(x)^n....  I am asking because Maple is able to solve many ODE's but some results contains unevaluated integrals such as the above.

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