## Cyclotomic Polynomials and Phi Functions

You'd think I'd be drawing circles in code because who doesn't love circles and pi? In reality though, I'm just writing Phi Functions today. It's some cool shit that's one thing for sure. But what exactly is a Phi function?

## Phi Function aka Euler's Totient Function

I never really understood the relation between Phi and Phi functions. Especially since the derivation of a Phi function is based on coprimes and Phi derives from Fibonacci. The cool thing about the Phi Function is that it counts only numbers that are "relatively prime" to the number inputted. So let's say you put in 15 into a Phi function. Then you're left with the set {1, 2, 4, 7, 8, 11, 13, 14}. Since there are 8 remaining numbers. Phi(15) = 8.

## A Snippet of code to show how it works

At first when I coded this. I wondered why sometimes it worked and other times it didn't. It turned out that I needed to count a prime only once in the case if it were to have multiple primes for the same numerical divisor. Confusing at first, I know, especially when dealing with prime numbers that have no divisors LOL!

## Cyclotomic Polynomials

Cyclotomic Polynomials on the otherhand take Phi Functions up a notch by each nth order it increases by. It's defined by Primitive Roots of Unities which is something we will discuss in another blog post.