Chapter 7.4, Problem 9P

In Problems 3 to 12, find the average value of the function on the given interval. Use equation (4.8) if it applies. If an average value is zero, you may be able to decide this from a quick sketch which shows you that the areas above and below the $x$ axis are the same.

${\sin }^{2}3x$ on $(0,4\pi )$