Indeed. I noticed that you posted this under calculus. I certainly wouldn't recommend the Principia as a reference for this. You could try Newton's Method of Fluxions for historical curiosity. I made it through about 70 pages of the Principia over the course of several weeks a few years ago before deciding it was too much effort at the time. Someday maybe...
You might look into Newton's Principia for the Common Reader in which Chandrasekhar analyzes Newton's propositions. I haven't given it a go yet, but if I tackle the Principia again that is probably the book I'll choose, at least as a companion.