Your pi(tau) is an unknown function of tau. How can it be possible to solve for tau an equation that contains an unknown function of tau? The only thing that remove_RootOf does in this case is return your original equation. RootOf is just Maple's way of expressing inverse functions. It always uses _Z as its bound variable.

@nm You made a very valuable comment about StackExchange, and I was just about to respond to it, yet now you've deleted it! Please stop doing that!

Unless there's just by chance some physicist reading this who has the specialized knowledge required, the only way that you're going to get any help here is by posting your failed attempts. If the failure is due to a lack of understanding of Maple, it's very likely that we can help. If it's due to something else, it's much less likely.

@DJJerome1976 It is very difficult to program a command to make use of assumptions. The only ones that solve can handle are directional inequalities. The help page that acer linked implies that in the case of directional inequalities, the useassumptions option is equivalent to the method that I showed.

@nm Please stop deleting your Answers! You do this very often. In this case, there was nothing wrong with your Answer. It did the same thing as my Answer in a different way. It's likely that for some readers your way would be more understandable than my way, or that the combination of Answers would reinforce the learning.

@DJJerome1976 The lprint is not needed to do the job; it's merely there to help you understand the next line of code. That next line of code will work in all cases; it's not specific to your case.

It's despicable that you've deleted your Question after one of our volunteer experts went through the trouble of answering it for you. And to top it off, you've left this ugly and meaningless name "1111..." in our index.

@MapleEnthusiast I've been following that other thread. Unfortunately, I don't have any constructive input at this time.

@michele The symbol interactive has no predefined value when a Maple session is started. That changes when you use with(plots) because the plots package has an interactive command. So, when you use the symbol interactive for DrawGraph, you need remove any value that it has acquired. Prefixing any symbol with : - means that the reference is to the global symbol rather than to any package's symbol. Enclosing it in single forward quotes means to ignore any value that has been assigned to the symbol.

@acer Oh my, I have a feeling that this will become a FAQ.

@mthkvv It's not possible to calculate a middle coefficient of the product without fully scanning all coefficients of the multiplicands. But for leading or trailing coefficients, the simple fact that you"ve converted the multiplicands to lists already means that you've ruined any possibility of efficiency. To be efficient, the algorithm must only access the necessary coefficients of the multiplicands. 

I agree that it would be useful to have an efficient stock method under modp1 to compute the first n leading or trailing coefficients of a polynomial multiplication. An algorithm to do this is straightforward and elementary. It may be possible to implement this using only Maple-level code (meaning no need to touch compiled code), so one of us may be able to do this.

@vv Unfortunately, there are a few structures whose constructors have names that are different from their zeroeth operand. The zeroeth operand of a set is set, but the constructor is `{}`. This is an oversight because the only reasonable reason to use op(0, expr) as a function prefix is to access the constructor. What would be the point of avoiding a large set by returning an even larger function? 

Surely this is a bug in Grid. The set(...) appears to be an "escaped" internal intermediary format used before conversion to an ordinary Maple set. It's hard to imagine any good reason that it was programmed like this even if it worked correctly. It seems like a huge waste of memory that could make it impossible for Grid:-Map to return the multi-million-element sets of lists of tuples that you require.

By the way,  CodeTools:-Usage, when applied to a Grid command, doesn't return meaningful numbers, except possibly for the real time. The other numbers only apply to the master process.

@nm The command-line options are documented on help page ?maple. I don't have access to a computer at the moment, so I can't check whether standalone is mentioned there.