So it can really simplify sometimes, taking a derivative, and sometimes, you'll see on exams, these trick problems where you have this really hairy thing that you need to take a definite integral of and then take the derivative, you just have to remember the fundamental theorem of calculus, the thing that ties it all together, it connects derivatives and integration, you can just simplify it, by realizing that this is just going to be, instead of a function lowercase f(t), it's going to lowercase f(x), 