Here is your code rewritten slightly soas to do what you want:

 

f:=proc(n)
option remember;
if n=0 then 0
elif n=1 then -7*x^2
elif n>1 then -3*f(n-2)^2+(n+21)*cos(2*f(n-1))
end if

end proc:

f(18) is avery complicated expression as you might expect.

Easier:

f:=proc(n)
option remember;
f(0):=0;f(1):=-7*x^2;
f(n):= -3*f(n-2)^2+(n+21)*cos(2*f(n-1))

end proc;

 

You cannot say x = -R.. R and assume x > 0; that is a contradiction. Perhaps you mean alpha > 0, beta > 0? With those changes the problem becomes consistent at least. You also assume that the reason Maple is not giving you the answer is because the limits are symbolic. That is not true. If you substitute poitive real numbers for R, alpha and beta there is no answer from Maple. Maybe just a hard integral?

In case anyone else has this problem: It turns out that the Help pages use the DejaVu fonts and they were not installed on my computer. Little squares with question marks inside them were then substituted for the unavailble letters.  Downloading the fonts and installing them fixed the problem.

Hi, I can save a few names in a file to a new file that appears on my desktop and have been successful in reading in those names to a new worksheet. However, I have not been able to save my current worksheet and then read it back. I have tried the Export suggestion of Joe Riel to no avail. I have tried to save anames to a file but that does not work either for some very strange reason.(I have been able to do > xn:=aname('user'): >save nm, savtry10; and that works. Here is a toy example: a:=b^2+1; 2 b + 1 x:=sin(a); / 2 \ sin\b + 1/ y:=z->a*z-x*z^2; 2 z -> a z - x z save anames('user'), savtry9; Error, save can only save names # I do not see any error here. anames('user'); y, x, a save a,x,y, savtry10; #Note that this has worked! whattype(anames('user')); exprseq nm:=anames('user'); y, x, a save nm, savtry11; # Again, this has worked. Thanks for help and suggestions. rick