Question

CALC II - Surface Area
Find the area of the surface obtained by rotating the curve about the x-axis.

Answer 1

Any ideas?

Answer 2

Did you graph it on Wolf?

Answer 3

wolf?

Answer 4

wolframalpha.com

Answer 5

if a function y = f(x) has a continuous first derivative throughout the interval a<+x<+b, then the area of the surface generated by revolving the curve about the x-axis is the number
\[\int\limits_{a}^{b}2\pi y \sqrt{1+(\frac{dy}{dx})^2dx}\]

Answer 6

but I never get a result that matches the options doing it that way

Answer 7

Have you tried it before?

Answer 8

yeah, and it doesn't tell me what i did wrong..

Answer 9

What did you get for the first derivativE?

Answer 10

2-1/x

Answer 11

It should be 1/2x-1/x

Answer 12

hmm,

Answer 13

I don't have much time before this expires, should I try b as more or less an educated guess?

Answer 14

Hang on for just a little while longer. I'm entering it into a calc app to integrate it.

Answer 15

It says 605.216 pi

Answer 16

I got 1224 for the first one so based on that, if i didn't have time to check the rest, I'd choose the 4th one.

Answer 17

no. That is not right. Have you chosen it yet?

Answer 18

mk, thanks, I'll let you know how it goes, I have 7 problems to go before I see the score

Answer 19

not yet

Answer 20

I'll keep working on it. If I get it I'll post it.

Answer 21

mk, I'll work on these last few

Answer 22

It's the third one.

Answer 23

It's just a different form of the Wolfram answer which is 137.216 pi

Answer 24

ok,

Answer 25

I'll try that, now just 5 more :/

Answer 26

good

Answer 27

see, here is another confusing one

Answer 28

I can't get that one. Sorry

Answer 29

can you help with this one?
http://openstudy.com/study#/updates/4f52bb10e4b019d0ebb05825