Areas of solids of revolution by disk, washer, and shell?

Hey there, my question is, what are the guidelines (if any) to approach calculus problems like the ones I mentioned? I have difficulty trying to figure out which method to use... The most complicated are washers and shells, simply because both figures look the same to me, any advice or links are welcome. Thanks!Areas of solids of revolution by disk, washer, and shell?
In mathematics, the key principle is, ';Don't let your eyes fool you..'; Don't look..





When the strips that you chose are PARALLEL to the axis of revolution, then you will have a shell, also called cylinders.. If the strips are PERPENDICULAR, then you will have a disk, also called washer.. So the two methods are the cylindrical shell (choosing the strips to be parallel to the axis of revolution) method and the disk-washer method (choosing them to be perpendicular).. Don't be fooled with how these guys look.. Looks fool..Areas of solids of revolution by disk, washer, and shell?
Volumes--not areas--of solids.
The disk method is the same as the washer method, actually. Now, the washer and shell methods actually yield the same results. Any solid produced by rotation of an area can be done either way! Just make sure that, whatever method you use, you set up the integral correctly. Now, the problem is that one method might give you an easy integral to compute, whereas another method might give you a very hard one to compute. The question is, ';can you compute the integral?';!!!