April 2009 - 3b

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!