I know this can be pretty confusing. So even though this is real simple, don't feel bad for asking this because I had trouble with it also. It would be insanely long to explain everything, and it might be confusing also. So I will just give you the answer for now. One tip is that the four angles are equal to 360 degrees and the corresponding spot of an angle on the other line will be the same. So the answer is 44 for Angle Y.
The unit disk can be parameterized by the function
where and . The squared distance between any point in this region and the point (1, 1) is
The average squared distance is then going to be the ratio of [the sum of all squared distances between every point in the disk and the point (1, 1)] to [the area of the disk], i.e.