Obviously, calculus teachers have calculus mastered. How do they do it? Some people say that it's because they've been teaching calculus for years, but keep in mind that plenty of calculus teachers already seem to have the calculus mastered right before they start teaching. Seems to me like taking Calculus 1, 2, and 3 over and again (basically repeating the courses a bunch of times) is the only way to get that level of mastery. But I doubt anyone's going to do that. So how do the teachers know calculus so well? Do they just wake up their first day of teaching calculus and magically know everything?