So we could rewrite this. This is equal to one minus cosine theta over two times one minus cosine squared theta. Now, this is a one minus cosine theta, this is a one minus cosine squared theta, so it's not completely obvious yet of how you can simplify it, until you realize that this could be viewed as a difference of squares. If you view this as, if you view this as a squared minus b squared, we know that this can be factored as a plus b times a minus b. So I could rewrite this. This is equal to one minus cosine theta over two times, I could write this as one plus cosine theta times one minus cosine theta. One plus cosine theta times one minus, one minus cosine theta.