I used circles as my pupils and irises because they look round. I used hyperbolas as the under part of my eye and as the curvy bits on my bow tie. I used ellipses for my bow tie and my nostrils. I used a polynomial function for my chin because I have a slight chin cleft. I used inverse parabolas for the sides of my face and the round bits on my nose. The bottom of my nose is a cos graph because it curves into my nostrils nicely. I think that I went above and beyond because I shaded in everything on my face and neck except things that I wanted white.
My reference photo:
My graph of me: