- #1
TheKracken
- 356
- 7
Homework Statement
Find the area given by y=x^2, y=4, x=0 and revolved about y = -2
Use either the washer or shell method
Homework Equations
Shell; integral from a to b of 2∏x(f(x))dx
The Attempt at a Solution
Alright so I tried to do this is terms of dy so since we are revolving about y=-2 which would be the horizonal axis. I got x= sqrt(y) and then I set up the integral from 0 to 4 of 2pi(y-2)(sqrt(y))dy
but this seems to be giving me a volume of 0 which means I've got to be doing something wrong!
I also attempted it with a dx and I decided to use the integral from 0 to 2 of 2 pi(x-2)(4-x^2)dx but received a value of 0 as well! I feel like this means that I am doing something consistently wrong which is kind of good, but I would like to fix that.
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