Where are math.py and sys.py?

Where are math.py and sys.py?

I found all the other modules in Python33/Lib, but I can't find these. I'm
sure there are others "missing" too, but these are the only ones I've
noticed. They work just fine when I import them, I just can't find them. I
checked sys.path and they weren't anywhere in there. Are they built-in or
something?