Now what is this? Well, what we have here, this is just cosine squared of x. This is just sine squared of x. And we know from the Pythagorean identity, and this really just comes out of the unit circle definition, that cosine squared of x plus sine squared of x, well that's going to be equal to one for any x. So all of this is equal to one. And so we end up with one over cosine squared x, which is the same thing as secant of x squared. One over cosine of x is secant, so this is just secant of x squared.