The upper curve is and the lower curve is x-axis: . Thus, .

Note is proportional to the distance, which is . Which just means , for some constant (non-zero hopefully) of proportionality . Here use polar transform.2) A lamina occupies the part of the disk x^2+y^2<=100 in the first quadrant. Find its center of mass if the density at any points is proportional to the D of its distance from the origin.