Cosine of six, six pi. Cosine of six pi minus, minus cosine of 11 pi over two. Cosine of 11 pi over two. Well what is cosine of six pi going to be? Well, cosine of any multiple of two pi is going to be equal to one. You could use six pi as we're going around the unit circle three times. So, this is the same thing as cosine of two pi or the same thing as cosine of zero.