Hi. I have a function defined like this: 

myfun := proc(a11 ......)

f := a11 * x^2 + 2*a12*x*y + a22*y^2 + 2*a13*x + 2*a23*y + a33;
printf("\n");
 printf("%a",f);

 end proc; 

When i call this function from my worksheet, the "f" polynomial is printed unformatted. For example the output in my worksheet is

x^2+6*x*y+y^2-2*2^(1/2)*x-6*2^(1/2)*y-4

I have Maple 15. I am trying to calculate the limit of this function

((x^3-2x^2+sin(x))^(1/3))/(6x+2)

for x tend to +infinity. As you can get it with a rapid manual calculus, this limit is 1/6. But Maple returns undefined for this very simple limit. Why? How can i get Maple to calculate limits correctly? Derive 6 return the correct answer