If you look at the divisions being made, its pretty clearly based on how people would look for books. For calculus, lots of people buy books based on classes t

If you look at the divisions being made, its pretty clearly based on how people would look for books. For calculus, lots of people buy books based on classes they take. Hence the division. No one of any mathematical repute or who took anything beyond calculus would be confused by this so I'm okay with the menu as is.