## Couldn't solve the following using Maple....

I have been trying to solve the following question using Maple for quite some time but couldn't do it. Any guide will be highly appreciated.

P.S: I have just started learning it by myself in the last few days. I have been following An Introduction to Modern Mathematical Computing: With Maple. If you could suggest a more useful text, that would be helpful.

## Warning: Solutions may have been lost; Pleas help...

Warning: Solutions may have been lost;  Pleas help, i have uploaded .mw file

## Bad resolution for maple 2021...

How I have used maple 2018, 2019 and 2020. I am now trying to switch to 2021, however the resolution is irritating. The resoluion in the palettes tab is bad and is especially bad for the "popup suggestion window" when you press escape on like "sum" or "e". I have tried searching on google to fix it but have not been able to find any help. Using windows 10

The pictures attached shows the resolution problem.

I know it is a small issue, but it annoys me a lot. So any suggestions to what I could do?

## Activation code ...

Where should I put the activation code !

## Plotting a function with if statement does not wor...

Dear forum,

my name is Klaus, I am a former mathcad-user and new to maple. I try to get some sheets converted and found a maple-behaviour I don't understand.

I made up a simple function with an if statement. When I try different inputs by hand, I get correct results.
But if I try to plot it, I get the message that the if-statement does not work.

My question : How can I solve this ? And what is the difference between plotting a function and entering values manually ?

restart;
with(Units[Simple]);

funktion := x -> if 2*Unit('m') < x then 1/x; else 2*Unit('m'); end if;

r1 := 3.0*Unit('m');

r2 := 6*Unit('m');

plot(funktion(x), x = r1 .. r2);
Error, (in funktion) cannot determine if this expression is true or false: 2 < x*Units:-Unit(1/m)

## Extracting multivariable polynomial coefficients...

I have encountered the problem of extracting multivariable polynomial coefficients, such as using the remove command,

eq2 := 3*p^4*a[2]^2+6*p^2*q^2*a[2]*b[2]+3*q^4*b[2]^2+p^4;
eq2 :=convert(eq2,list);

eq2 := [3*p^4*a[2]^2, 6*p^2*q^2*a[2]*b[2], 3*q^4*b[2]^2, p^4]

map(t->remove(has,t,{p,q}),eq2);
[3*a[2]^2, 6*a[2]*b[2], 3*b[2]^2, undefined]

eq3 := 3*p^4*a[2]^2+6*p^2*q^2*a[2]*b[2]+3*q^4*b[2]^2;
eq3 :=convert(eq3,list);

map(t->remove(has,t,{p,q}),eq3);

[3*a[2]^2, 6*a[2]*b[2], 3*b[2]^2]

Because the term p ^ 4 similar to power appears, a program should be written to calculate it,      Programming

extractxishu:=proc(p)

local i,xishulist,teamlist;

teamlist:=convert(p,list);

xishulist:=[]:

for i in teamlist do

if type(i,`^`) then

xishulist:=[xishulist[],1];

else

xishulist:=[xishulist[],remove(has,i,{p,q})];

end if;

end do:

end proc:

Inspection procedure:

eq2 := 3*p^4*a[2]^2+6*p^2*q^2*a[2]*b[2]+3*q^4*b[2]^2+p^4*c[3]+p^3*q*c[3]+6*p^3*a[1]*a[2]+6*p^2*q*a[2]*b[1]+p*q^3*d[3]+6*p*q^2*a[1]*b[2]+q^4*d[3]+6*q^3*b[1]*b[2]+p^4+4*p^3*q+p^3*c[2]+6*p^2*q^2+p^2*q*c[2]+6*p^2*a[0]*a[2]+3*p^2*a[1]^2+6*p^2*a[2]*b[0]+4*p*q^3+p*q^2*d[2]+6*p*q*a[1]*b[1]+q^4+q^3*d[2]+6*q^2*a[0]*b[2]+6*q^2*b[0]*b[2]+3*q^2*b[1]^2+p^2*c[1] +p*q*c[1]+p*q*d[1]+6*p*a[0]*a[1]+6*p*a[1]*b[0]+q^2*d[1]+6*q*a[0]*b[1]+6*q*b[0]*b[1]+p*c[0]+p*d[0]+q*c[0]+q*d[0]+3*a[0]^2+6*a[0]*b[0]+3*b[0]^2            extractxishu(eq2);

The result is incorrect  ， It is found that the command is successful in a separate calculation, but extractxishu is invalid in the program. Why?

Can any expert tell me where this mistake is? How to modify this program!

## Local vs. global variables ?...

Can someone tell me why there is a difference between global and local variables in this code?

...cannot determine if this expression is true or false

GlobalLocal.mw

## No update result pressing enter...

Maybe I am missing something here. Maybe it's just a new feature?

I have just installed Maple 2021 on Mac.

A simple sheet, using simplify-simplify to get units right.

Sometimes Maple doesn't update result when pressing Enter.

Sometimes Maple doesn't give any result when pressing Enter.

First everything ok:

Then I change a to 5 m. Pressing Enter on all three lines gives:

The value of A is not updated.

If I then delete the 'simplify 9 m^2' and presses Enter on the line with A:=a*b, there is no output?

Pressing Enter on blue line, no output.

## Non-autonomous ODE linearization...

Given:

x'=-(1+0.1sin(10t))*x+1

https://www.wolframalpha.com/input/?i=x%27%3D-%281%2B0.1sin%2810t%29%29*x%2B1

I need to linearize this non-autonomous differential equation at the equilibrium point (which, according to numerical simulations, is present).

I am familiar with the usual approaches through the Jacobi matrix, but how to use this tool in the case of non-autonomous equations is not clear.

## Documentation for ChangeCoordinates?...

Reviewing the help Physics Examples worksheet Section 1, subsection 5 a transformation between cartesion and spherical coordinates is defined using the command ChangeCoordinates from the Physics[Vectors] package. This command is described briefly as follows in the Updates, Maple 2015, Physics page:

"New command: ChangeCoordinates, to rewrite an algebraic expression, using Cartesian, cylindrical, and spherical coordinates, an expression that involves these coordinates, either a scalar expression, or vectorial one but then not changing the orthonormal basis."

However, when I use the link to the ChangeCoordinates help page, the link simply loops back to the Updates, Maple 2015, Physics page.  Is there a specific help page for the ChangeCoordinates command?

## A problem about 'proc, coeff, diff'...

The file is attached.

The command 'coeff' doesn't work.

## Combine two plots...

Hi!

I am trying to combine the plot in cobweb-diagram.mw (sorry for the messed up axes, you can adjust it in the 'axes properties') with the plot in modèle_graphes.mw. I've tried these two things : test1.mw and test2.mw, but I can't make it work.

## Delta. ...

How do I make my Maple use delta instead of d for differential equations?

example:

## nested Tabulate...

The Document Tools, Tabulate command says this:

Calls to the Tabulate command cannot be nested within each other unless used with the option output=XML and other DocumentTools commands to construct your own content.

Is there an example of nesting Tabulate commands using output=XML ?

Thanks

## Trying to collect tdeg. coefficient of multivariat...

I have a polynomial in c & d.  I wish to extract the coefficients of lets say 3rd order i.e c^3+c^2d+c d^2+d^3.

The polynomials can be of 2,3,4.. variables.

coeffs(14*c^4 + 84*c^3*d + 180*c^2*d^2 + 165*c*d^3 + 55*d^4 + 5*c^3 + 21*c^2*d + 28*c*d^2 + 12*d^3 + 2*c^2 + 5*c*d + 3*d^2 + c + d + 1, [c, d], 'l');
14, 84, 180, 165, 55, 5, 21, 28, 12, 2, 5, 3, 1, 1, 1

l[1];
4
c

l[2];
3
c  d

l;
4   3     2  2     3   4   3     2     2   3   2        2
c , c  d, c  d , c d , d , c , d c , c d , d , c , d c, d , c, d,

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