You're right. The boundaries are not clear to me either.
http://www.wolframalpha.com/input/?i=plot+y%3D2sinxcosx%2C+y%3D2cosx
Find the volume generated by rotating about the x axis the area bounded by x=0, y=2sinxcosx,, y=2cosx, and x=4, if 0≤x≤pi/2.
I don't get the graph.
2 answers
y=2sinxcosx=sin2x