Question

how do we express our answers in terms of pi

Answer 1

well say you have a circle with radius of 5cm

and you know the Circumference of a circle equals 2 times pi times the radius

\(C=2\pi r\)

you would find that the circumference = 10π cm

notice how pi remains in the answer
(this means the answer is expressed in terms of pi)

Answer 2

if instead, the question asked for you to express your answer as an approximation
you could use π≈3.14

and you answer would change; C=10π cm ≈ 31.4 cm