F of g of x. And I encourage you to pause this video and try to work it out on your own. Well, one way to think about it is the input into f of x is no longer x, it is g of x. So everywhere where we see an x in the definition of f of x, we would replace with a g of x. So this is going to be equal to, this is going to be equal to one plus, instead of the input being x, the input is g of x, so the output is one plus g of x. And g of x, of course, is cosine of x. So instead of writing g of x there, I could write cosine of x.