Science talk:Math Exam Resources/Courses/MATH101/April 2009/Question 3 (b)

The answer displayed is pi integral ((arccos(y))^2 + 2arccos(y)) dy. Shouldn't it be pi integral ((arccos(y))^2 + 4arccos(y)) dy?

I thought:

(arccos(y) + 2)^2 - 2^2

= (arccos(y))^2 + 4arccos(y) + 4 - 4

EDIT: this would lead to the pi^2 + 2pi answer that Amy got.

Yes, you're right! Solution is updated now. Thank you!

For the answer of this question, I was practicing my integration and instead of the answer pi squared, I got pi squared + 2pi. I was wondering whether is correct or not.

Hello Amy. Wolframalpha says it's π². If you want to post your steps we can see where you went wrong. Your answer is not far off, so probably you just overlooked a minor thing?

In the solution, should there be a pi in front of the integral when finding the volume?

Yes! Good catch, thank you. Fixed now.