Question

What is pi and where it is used

Answer 1

pi is used to measure circle.
circumference of a circle by diameter divide!

Answer 2

pi (π) is the ratio of the circumference of a circle to its diameter. in other words pi equals to circumference divided by the diameter(π=c/d).
it's used to find the perimeter and area of a circle.
perimeter of a circle=2πr
area. ". ". =πrsquare