## Error while solving PDE...

Hi,

While trying to run this code :

```pde := diff(u(x, t), t) = k*diff(u(x, t), x, x);
bc := u(x, 0) = T, u(0, t) = a*t + b, u(L, t) = T;
pdsolve([pde, bc], u(x, t)) assuming (0 < k, 0 < L, 0 < a, 0 < b, 0 < T, 0 <= t, 0 <= x and x <= L);```

I get the following error :

Error, (in assuming) when calling 'factor'. Received: 'floating point coefficients are incompatible with field extension; use 'real' or 'complex' instead'

Any idea why ?

## check inequality with Maple...

Assume I know some relations like 0<a<b<c<1, n is positive integer, and I want to know if

holds. How to check this in Maple? Is there any command like verifiy evalb for this kind of problem.? Or solve the inequality in terms of c, given the relations of a,b,c?

Thanks.

## Contour plot in polar coordinates...

Hi, I'm trying to plot equipotential lines and streamlines in Maple, and both equations are in polar coordinates. I can plot a contourplot in cartesian coordinates, but adding "coords=polar", it throws an error. I tried to write a do loop but it wasn't having it either. any help would be appreciated

restart; with(LinearAlgebra); with(plots);
K := 1;
psi := K*r^(4/3)*sin(4/3*theta);
phi := K*r^(4/3)*cos(4/3*theta);

p1 := contourplot(psi, r = 0 .. 1, theta = 0 .. 3*Pi*(1/8));

p2 := contourplot(phi, r = 0 .. 1, theta = 0 .. 3*Pi*(1/8));
display(p1, p2);

## which version of maple start to support Grid Compu...

which version of maple start to support Grid Computing Toolbox?

## Where does the label "spam" come from?...

It has become more and more common to meet questions as labelled as "Spam". What does this classification mean?
Strangely if you click on the little red flag "Spam" it even seems that you can delete the corresponding question.
Does it mean that some people here have the power to decide if a question deserves to be answered or merits to be put on the trash?
Given that these questions are answered the same way than any other non spam labelled question, why are they labelled as spam?

## Maple procedure to find the solutions to a cubic...

Hi I need to write procedure to find a cubic equation... anyone could help me ...?

## simpliy calculate...

Hello

Every time im working with maple and answer is in term of sin or cos maple dont calculate them for example it give me sin(pi/2) but i want it himself know that sin(pi/2)=1 some times i use of [eval] but it again dont calculate it what i should do?

## Generate Matrix Directly...

Generate Matrix Automatically for solving Higher order Differential Equation For Chebyshev Polynomial

## Differential with respect by which parameter...

What is the concept of these terms?

(D[2, 2](T))(x, 0) = 0, (D[1, 1](T))(x, 0) = 0 ? I want to know these terms show

with respect by which parameter?

## How to remove summation from both sides?...

At a point in a worksheet I end up with an equation that has summations on both sides.  The range of summation is the same but the summands are different.  I want to remove the summations from both sides, keeping the equation with just the summands. How can this be done?  The only way I have found is to manually select each summand with the mouse and paste it into a new line which breaks the 'automation' of the script.

## simplify expression to complete derivative...

This

`expr:='1/r^2*diff(r^2*diff(v(r),r),r)'`

gives

And when evaluated second time it gives

`expr`

The question is, how to put expr back to its original form shown at the top?

I tried simplify, combine, etc.. but nothing puts back to same form.

The reason I am asking, is that I need put more complicated expression in form that resembles when I am looking at in textbook. For an example, the Laplacian

```VectorCalculus:-Laplacian(u(r,theta,phi),'spherical'[r,theta,phi])
```

But the above should be the same as

So I figured if I can rewrite each term to look like in the shorter version above (complete derivative version), it will be easier for me to compare what Maple gives and the text book shows,

ps. I found that the following command in Maples gives a little clearer Laplacian, but it is still not as simplified as the book but it is better than using VectorCalculus:-Laplacian

```Physics[Vectors]:-Laplacian(u(r,theta,phi));
```

At least this has each term a little more seprated.

## Discontinuities even with "discont=true"?...

Hello everyone,

Even using the command "discont=true", some of the functions I plot still present discontinuities, but some of them do not present.

How can I fix this? This one file ilustrates perfectly the problem.

file_discont.mw

## auto legend for plot...

Is there any way to automatically create a legend for a plot of a list of functions? The problem is, I'd rather not specify the legend and maple require the exact number so I cannot specify a generic length such as [1,2,3,4,5,6,7,8].

plot([f1(x), f2(x), f3(x), sin(x)*cos(x)*sin(3x^2 + cos(x))], x=1..34)

The point is that I do not want or care what the legend is(except the names shouldn't be long). I just want to be able to use it to select the plots easily and to be able to reference them(so the naming matters in that the order shoudl be obvious).

## Closed geodesics at regular tetrahedron...

Hello. I can not realize such a thing. There is an equal tetrahedron NET on the plane. Choose a point on the edge and start a vector from it (the sum of red vectors with some integer coefficients). We obtain a closed geodesic. Depending on the coefficients, the geodesic will intersect the edges and faces in a different sequence. How to unNET into tetrahedron and so that the geodesic is displayed on it? Thank you in advance.