Can't post this reply

[stapel]

Sorry about the confusion, I am trying to find the volume of the solid that is generated. I am aware that that I need to find the outer radius and the inner radius, although i am having trouble with finding these. From what I worked I got that the outer radius is 1+e^y and the inner radius to be 1. When I set up the integral I get something along these lines

The integral from 0 to 1 pi[((1+e^y)^2)-((1)^2)]dy

I think your derivation was something along the lines of the following:

. . . . .converting outer-radius function: y = ln(x) => x = e^y

. . . . .outer radius: R = ey - (-1) = ey + 1

<< MISSING LINE GOES HERE >>

. . . . .do volume by discs: outer circle's area, less inner circle's area,
. . . . .multiplied by tiny widths delta-y = dy, and summing areas

. . . . .sum of (pi R² - pi r²)*(delta-y) => int[0,1] pi(R² - r²) dy

Your integral looks good to me.

 

[stapel]

Missing line about radius that's causing forum's script to choke:

\(\displaystyle \mbox{inn}\mbox{er rad}\mbox{ius: }\, r\, =\, 0\, -\, (-1)\, =\, 0\, +\, 1\, =\, 1\)

In the original, the above was plain text, like the rest of the post. I had to munge things via LaTeX to get it to post.

Any idea what's going on?