So let's say that we have f of x is equal to x squared over cosine of x. Well, what could be our u of x and what could be our v of x? Well, our u of x could be our x squared, so that is u of x and u prime of x would be equal to two x. And then this could be our v of x. So this is v of x and v prime of x. The derivative of cosine of x with respect to x is equal to negative sine of x. And then we just apply this.