Pi is used to find the circumference and area of a circle. It is also used to find the volume and surface area of a sphere, cone and cylinder. Pi has applications that go beyond geometry as well, such as statistics and probability.
For example, it is used for calculating normal distributions and the distribution of prime numbers. It is also used in Buffon’s Needle Problem. This proof determines the probability of a needle landing on a line when it is dropped onto a plane containing equally spaced parallel lines. Pi is also prominent in geometric constructions and some formulae involving limits.