Please try uploading  your file again.

Do not post the same thing in both Posts and Questions. This is obviously a Question. Posts are mostly expository.

@maple2015 Your equation can be easily solved. Maple is fully prepared to deal with complex-valued solutions, often with no additional effort required by the user. Indeed, it often works more naturally with complex-valued functions than with real-valued ones. Your complex solution can be easily split into real and imaginary parts using commands evalc, Re, and Im. Those parts will both be real-valued functions. This will also often cause the appearance of sin and cos in the solution. You can also use convert(..., sincos) to force re-expression in terms of sin and cos.

@maple2015 Yes, that's correct, there's no way to get a purely real-valued solution under those circumstances. This is a mathematical limitation, not a Maple limitation. You seem surprised by this. Why? The space of complex-valued functions is much larger than the space of real-valued functions, so it's no surprise to me.

@mmcdara Here's my "external eye": In the first case, you've used solve on an equation that contains radicals. In the second case, you've used solve on a non-radical polynomial equation derived from the radical equation. As is very well known, that process has the risk of introducing extraneous solutions. Those solutions need to be verified in the original equation.

I don't see any Maple bugs revealed by your worksheet.

@elen

Are you trying to right-click on the input (the black text) or the output (the blue text)? It should be the output.

Disclaimer: I don't know if the following test will do anything in your Maple 13:
========= Test that works in modern Maple =================================
As a diagnostic for your situation, try this. Let expr be the equation or expression for which you are trying to get a context menu. Then type this command:

ConxtextMenu:-Test:-GetGeneratedMenuAndAction(expr);

and report here the results.

If (and only if) the expression was the most-recent thing that you typed in, you could also do

ConxtextMenu:-Test:-GetGeneratedMenuAndAction(%);
========== End of test that works in modern Maple ============================

Condidering the age of your Maple, you may need to learn to just type the commands rather than using context menus. We can help you with that here.

Try first using a left click to select the object for which you want a contact menu, then right click.

@radaar Nobody in this thread "confirmed that it won't converge"; there was merely skepticism expressed about it. For my part, I wanted a strong theoretical reason for its convergence before I spent considerable effort getting a numerical result, a result which would be worthless if it didn't converge.

The link to your uploaded worksheet doesn't work. (Probably not your fault.) Please try uploading it again.

@jessicalee You've done pretty good so far! You only need to change

for a to Onto do

to

for a in Onto do

You use to to set an integer upper limit for a; you use in to have a iterate through a list or set.

You can make a further improvement by changing the final semicolon to a colon. Then only the decrypted message will be printed.

By the way, have you noticed yet the pattern of which a make f(a) onto?

@Joe Riel The exact same double-forward-quote method occurred to me first also.

Please post your code in such a way that it can be copy-and-pasted into a Maple worksheet. You can either directly upload a Maple worksheet, copy-and-paste from a worksheet to a post, or simply type the code in a post.

@mmcdara Using unapply won't work if P is a procedure already defined.

I'm not on a computer right now to check, but I doubt that VV's solution works at all.

Expressions such as A ==> B and A <==> B only make sense if A and B are statements that have truth value, such as equations. So ln(x) + ln(y) ==> ln(x*y) makes no sense. An identity must be a "two-way" equality. (I mean that equality is necessarily a symmetric relation.)

I think that your Question should be titled "Decrypt message" rather than "Encrypt message".

We need to see how f(a) is defined in Problem 2.

@Hamid_Chohan 

M:= 5:
for i1 to M do
   N[i1, 0]:= 0;
   N[0, i1]:= 0
end do;

There is no reason to use an if statement for this.