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# C3 Integration Help Watch

1. Hi. I'm doing questions on volumes of revolutions, but am stuck since I am unsure how to integrate a few things, namely:

(4a^2 - 4ax)^1/2

and

(2lny)^2

I know how to differentiate when there are brackets like this, but not how to integrate.

Help would be much appreciated.

Thanks
2. You use the chain rule on both, but for the first one, treat a as a constant
3. (Original post by cpdavis)
You use the chain rule on both, but for the first one, treat a as a constant
Thanks. Also, when substituting 2 in for y once i've integrated, how would I simplify 1/3(2ln2)^3. ?
4. (Original post by Marisa_Grace)
Thanks. Also, when substituting 2 in for y once i've integrated, how would I simplify 1/3(2ln2)^3. ?
This isn't the right integral. What I should have suggested was to use parts. But you would break down the ln term in the differential and integrate a 1
5. (Original post by cpdavis)
This isn't the right integral. What I should have suggested was to use parts. But you would break down the ln term in the differential and integrate a 1
I don't really understand what you mean at the end. Also, when i integrated i got 1/3(2lny)^3 x 2/y.

6. parts to finish it off
7. (Original post by Pheylan)

parts to finish it off
you've explained it better

Sorry OP if the last bit I said was a bit unclear
8. .....or if you are feeling really adventurous try deriving the reduction formula for (ln x)^n....

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