For each of the surfaces, calculate its exact area.

b) The area bounded by the curves y = 4sqrt(x), y = 2x+2 and the x-axis. Use vertical rectangles.
c) Same curves but use horizontal rectangles.

Wouldn't using rectangles count as a approximate Riemann sum? Since they ask the exact area I was going to integrate the higher curve - the lower curve in the [0,1] bounds. I don't see how using vertical or horizontal rectangles is going to give me an exact fraction answer.

Thank you

for c) rectangles, you won't get exact area no matter how you do it, unless the width of the rectangles approaches zero.