It's a number - used in problems involving geometry.
I think it is
Pi is used anytime there is a circular (as opposed to linear) geometry involved. Examples include circles, cylinders, spheres, and other cruves.
The value of pi is the circumference of a circle divided by its diameter
The ancient Greeks did the original work of inventing geometry as we know it, and pi is a letter in the Greek alphabet, so it was a convenient symbol for them to use.
Circumference of a circle = 2*pi*radius or diameter*pi Area of a circle - pi*radius2
Specifically geometry. Pi is the numerical value of the ratio of the circumference of a circle to its diameter.
You cannot find the "PI" of anything Pi is a set numerical value, PI = 3.14159265358979323846… (It goes on forever) But in geometry we consider Pi to equal 3.14
surface area. S = 4 * pi * R2 This refers to the fluence around the surface
If you are meaning it in sense of a geometry, the it's 3 * 180 degrees (which is what they mean by pi) = 540 degrees.