dealing with non-calculable sums

[pluton]

Hi,

I'm working with Maple 13 and have command lines like:

> restart;
> A:=sum(sum(a(m,n)*cos(m*Pi*x)*sin(n*Pi*x),n=1..N),m=1..M);
> diff(A,x);

I have two questions:
1 - is there a way to tell Maple not to try to calculate this sum? Maple correcly goes through these two lines but it takes a lot of time.
2 - is there a way to change a(n,m) to a_{nm} (Latex notation for indices)without using the newly enriched command lines allowing for greek letters and all that?

Thank you

[acer]

For your question 1), you could use the inert `Sum` command instead of the active `sum` command. And then use the `value` command later on, if you wanted Maple to try and compute it.

Sorry, but I don't understand what you mean in your question 2). Are you asking about how you can type it in, as plaintext input? Or are you asking about internal representation? Or are you asking about display of output?

[pluton]

Thank you for question 1. For question 2, I just figured out that notation sum(sum(a[m,n]*cos(m*omega*t)*sin(n*omega*t),m=1..M),n=1..N); was fine.