And so now this is interesting. In fact, let me rewrite this. This is going to be equal to negative, the negative integral of one over cosine of x times negative sine of x dx. Now, does it jump out at you what our u might be? Well, I have a cosine of x in a denominator and I have its derivative. So what if I made u equal to cosine of x? u is equal to cosine of x and then du dx would be equal to negative sine of x.