Question: Error message when trying to plot graph

Hi!

I'm sure there is a simple solution to my problem, but because I'm fairly new to using Maple, I can't figure out why my graph won't work. All I'm trying to do is graph a function along with its first and second derivatives within the same graph. The original function is f(x)= (2+sinx)^x²/(x²+1).

I defined the function as f and then found the first derivative by using df:=D(f);. The second derivative I used d2f:D=(df);. Both derivative calculations came out just fine.

Then when I went to graph all 3, this is what I put:

plot({f,df,d2f}, -10..10);

And it gave me the error message of:

Warning, unable to evaluate the function to numeric values in the region; see the plotting command's help page to ensure the calling sequence is correct.

Any ideas on how to fix this? Any help is greatly appreciated, it's for a class assignment.

-Kyu