In the diagram, the smaller circles touch the larger circle and touch each other at the center of the larger circle. The radius of the larger circle is $6.$ What is the area of the shaded region?
The area of the larger circle is pi * radius^2 = pi * 6^2 = 36 pi (1)
The radii of the two smaller circles = 3
So...the area of these two circles is 2 * pi * (3)^2 = 18 pi (2)
So...the shaded area is (1) - (2) = [ 36 - 18 ] pi = 18 pi [ units^2 ]