Since the disk and the hole are symmetrical with respect to the axis, the coordinate of the center of mass of the upper half is the coordinate of the center of mass of the entire disk and hole. Therefore, only the upper half needs to be considered.
defines the difference between the disk's outer circle and the edge of the circular hole. This is the net surface area at .
The function is the total mass moment relative to .
Solving the equation for gives the abscissa of the center of mass.