I haven't soved yet why dchange is not working for this simple command. Any help out there?

Thanks a lot

I have a problem using dchange when my variable depend on two (or more variables) and I would like to apply the chain rule.

For example, when I use the command

I would expect something like 

But I get an error saying that the number of new variables and transformation equations must be the same.

Any idea how I could solve it? 

Thanls a lot for your help.

Hi,

Can somebody help me to find out why Maple can't completely solve this system of differential equations?

The answer to the previous command is

but I don't get the solution for u(x). This should be u(x)=-x+x^2/2.

Thanks for your help

I have the following code in Maple 13:

SYS := {diff(T(x, t), t) = diff(T(x, t), x, x)};
IBC := {T(1, t) = 0, T(x, 0) = 1, (D[1](T))(0, t) = -exp(t)};
SOL := pdsolve(SYS, IBC, numeric, time = t, timestep = 1/10);
R := SOL:-value(output = listprocedure); temperature := subs(R, T(x, t));

It integrates the heat equation in the interval x=0..1 and it seems to work ok.
However, I have problems trying to obtain the temperature derivative at the boundaries (this is at x=0 and x=1). I'm using different commands and it seems the derivative is evaluated ok inside the domain but not at the boundaries.
If I try
fdiff(temperature(x, t), [x], {x = 1,t=0.5});

or

evalf((D[1](temperature))(1, .5));

I don't get any numerical answer. Any idea how I could obtain the value of the derivative at the boundaries?

Thanks in advance,

Javier

Hi everybody,

I would like to define a function with random values to be used in pdsolve (numeric) as a initial condition.

Any help?

Thanks,

Javier