To perform the calculations for the circumference and area of a circle, you may have used the π key on your calculator. When you press this key, the screen of your calculator shows more digits than the 3.14 you use as an approximation for pi.
Actually it goes on forever. There is no exact value for this irrational quantity.
What is the exact value of pi?
The exact value of pi is 3.1415926535897932384626433832795028841971693993751058209749445923078164062862089986280348253421170679.