We're given a differential equation right over here, cosine of y plus two, this whole thing, times the derivative of y with respect to x, is equal to two x, and we're given that for a particular solution, when x is equal to one, y of one is equal to zero. And we're asked, what is x when y is equal to pi? So the first thing I like to look at when I see a differential equation is, is it separable? Can I get all the y's and dy's on one side, and can I get all the x's and dx's on the other side? And this one seems like it is. If I multiply both sides by dx, where you can view dx as the x differential of an infinitely small change in x, well then you get cosine of y plus two times dy is equal to two x times dx. So just like that, I've been able to, all I did is I multiplied both sides of this times dx.