So once again, the way we denote the area is the definite integral from pi over 2 to 3 pi over 2 of cosine of x dx. The antiderivative, or an antiderivative of cosine of x is sine of x evaluated at 3 pi over 2 and pi over 2. So this is going to be equal to sine of 3 pi over 2 minus sine of pi over 2. What's sine of 3 pi over 2? If you visualize the unit circle real fast, 3 pi over 2 is going all the way 3 4ths around the unit circle. So it's right over there. So the sine is the y-coordinate on that unit circle.