So the way you remember it is you have these two things here. You're going to end up with two different terms. And each of them, you're going to take the derivative of one of them but not the other one. And then the other one, you'll take the derivative of the other one but not the first one. So derivative of u times v is u prime times v plus u times v prime. Now when you just look at it like that, it seems a little bit abstract and that might even be a little confusing but that's why we have a tangible example here. And I color coded it intentionally so we can say that u of x is equal to e to the x and v of x is equal to cosine of x.