Hi, I have a question concerning solid of revolution. The bowl-shaped volume formed by rotating the area circumscribed between y=bcosh(1) and y=bcosh(x/a) around the y axis was given to us by the instructor as pi*b*int [x^2*d(cosh(x/a))] between 0 and a. My question is why are the integration boundaries not -a and a, but 0 and a, OR, alternatively, why wasn't the final answer then multiplied by 2? When the same area is rotated around the x axis the integration boundaries are indeed -a and a. Why aren't the boundaries similar in both cases?