In the following video TA describes radius of a shell as (6-x).

I don't understand why we even talk about x=6 since (4,6) is an empty region, and not just rotate around x=4 for the sake of determining the solid. Would not that result in exact same volume since (4,6) is empty anyway?

But the radius then would be (4-x), not (6-x). Am i wrong somewhere?

http://www.youtube.com/watch?v=MYXMC7koJyY

https://www.desmos.com/calculator/xoqm4izy6e

Question

In the following video TA describes radius of a shell as (6-x).

I don't understand why we even talk about x=6 since (4,6) is an empty region, and not just rotate around x=4 for the sake of determining the solid. Would not that result in exact same volume since (4,6) is empty anyway?

But the radius then would be (4-x), not (6-x). Am i wrong somewhere?

http://www.youtube.com/watch?v=MYXMC7koJyY

https://www.desmos.com/calculator/xoqm4izy6e

anonymous · Answer

Nvm I got it.