All About Pi The is a Greek letter which is the symbol for pi. This one is covered in multiple digits of pi. Created by: Logan Walker What is Pi?Pi is an irrational number that never ends. Pi is the distance around a circle with a diameter of 1 or half way around a circle with a radius of 1. For What is Pi Used?Pi is used to find the circumference of a circle, area of a circle, surface area of a cylinder, area of a cylinder, plus much more. Why is Pi Important?Without pi it would be extremely difficult if not impossible to find the area or circumference of a circle or any of the measurements of figures listed above. Who Recognized Pi First?The first person to recognize pi was William Jones. He did this in 1706. He was a mathematics (math) teacher. FinallyHappy pi 1 month late pi day from me!!!!!!!