Well, I could just substitute back. This is going to be equal to, I will write it like this, sine of u of x, which is three pi over two minus x, and I'll fill that in in a second, over cosine of u of x squared times u prime of x. U of x is three pi over two minus x. Three pi over two minus x. And then u prime of x, we already figured out is negative one, so I could write times negative one. Well, yeah, let me just leave it out there for now. I could have just put a negative out front, but I really want you to be able to see what I'm doing here. So now we want to evaluate at x equals pi over four.