(1)You can view the the region as subtracting the rectangle from the quater-circle.

Now the centroid of the rectangle is trivial (1.5,1.5) und the area is 9.

The centroid of a quater-circle is located on the line (that is symettry) and is (a known formula). In this case . Thus the centroid is . Thus, . And has area .

Thus, by the composite centroid formula we have,