F of x is equal to u of x times v of x, v of x. If we were to take the composition, if we were to say u of v of x, pause the video, think about what that is, and that's a little bit of a review. Well, this is going to be, I take u of x, takes the cosine of whatever is input, and now the input is v of x, which would be sine of x. Sine of x. And then if you did v of u of x, well, that'd be the other way around. It would be sine of cosine of x. But anyway, this is, once again, just to help us recognize, hey, do I have, when I look at an expression or a function definition, am I looking at products of functions?