How do you write your answer in terms of pi?

When the question says "Write your answer in terms of pi.", it means that if you

worked the problem correctly, then you had to use (pi) to solve it, and (pi) appears

in the answer you have. They're telling you that it's OK to just leave it that way ...

you don't have to keep going and figure out what the number is after you plug in

the numerical value of (pi).