is a circle with center at (0, 4/2) and radius 4/2 while r= 1 is a circle with center at (0, 0) and radius 1.

The two curves intersect where [/tex]r= 1= 9 sin(\theta)[/tex] or . For , that is satified by and .

For between those two limits, r ranges from 1 up to . The "differential of area" in polar coordinates is so the area is given by .