- #1
lionely
- 576
- 2
Homework Statement
The area enclosed by y= 4/x^2 , y =1 and y =4 is rotated about the x-axis; find the volume generated.
I am really confused I keep getting (14pi/3). But the answer in the back of the book is not that at all.
An additional question, the only method I know is drawing a really thin rectangle of width dx or dy depending on which axis I am rotating it about. The question is , does the rectangle always have to be at right angles to the axis of rotation?
Homework Equations
The Attempt at a Solution
Here my attempt with my little sketch graph. The area I am supposed to be rotating is confusing because of that gap in the graph . I chose x = 2 and x=1 as the limits because that is what I got when I put in y=4 and y=1 into the function. I thought about using x=-2 and x=x-1 as well and adding them but that just gives me 28pi/3 and that is not the answer either. I am quite confused..