The area of a sector of a circle with radius r and central angle is given by .
We can approximate the area bounded by the polar curve and the rays and by using sectors of circles.
First, divide up into n subintervals with endpoints and equal width .
Consider the subinterval and choose some .
The area on this interval is approximately the area of a sector of a circle with central angle and radius . So, .
Therefore, an approximation of the entire area is: .
Allowing the width of each subinterval to become infinitely small by letting n approach infinity, we obtain .
Thus, is the area of the region bounded by on .