What is the net area between #f(x) = cos2x-xsinx # and the x-axis over #x in [0, 3pi ]#?
The net area between
Using the DI method (an easier way to understand integration by parts):
Multiply the diagonals with the appropriate sign, and add them (and don't forget the negative sign in front of the integral from before):
That is the net area under the curve. Hope this helped!