An algorithm is the meat of a function. It’s the “how.”
And if you’re using someone else’s function, you won’t touch the “how” because you’ll be interacting with the “what.” (You use a function for what it does.)
You will be creating your own algorithm by writing code, however. Because an algorithm is just a sequence of steps that, taken together, constitute an attempt at achieving an objective.
Haus is saying all the little steps that go into approximating sine occur directly on the hardware.