Question

Can't wrap my head around the concept of finding the shell radius and shell height, when revolving around a line such as y=2. Any help?

Answer 1

here it is about y=0. So the radius will be from y=y0 to y.
https://www.khanacademy.org/math/ap-calculus-ab/ab-applications-definite-integrals/ab-shell-method/v/shell-method-for-rotating-around-horizontal-line
see if that helps.