What is the actual meaning of the notation of Code (Text): df[g(x)] ------- dx Here do we actually differentiate f with respect to x first and then evaluate it at g(x), or do we first evaluate f at g(x), then differentiate it with respect to x? Does the order matter? df --[g(x)] dx d --f[g(x)] dx Are these two equivalent to the first one? (i.e. do all three notations have exactly the same meaning?) Thanks for explaining!