Question

integration:

Answer 1

\[\int\limits (x^2+2x)cosx dx\]

Answer 2

@greenglasses can u help me with this one?

Answer 3

I'd start by splitting the integral into two pieces:
\[\int\limits(x^2cosx) dx + \int\limits (2xcosx) dx\]

Answer 4

Then I'd try integration by parts.

Answer 5

ohhh I see :) Thanks @greenglasses will give it a try now and I'll let u know

Answer 6

Do you know what the answer is supposed to be?

Answer 7

yes... but I can't come out with it :/

Answer 8

I'm getting \[-x^2sinx-xcosx-sinx-2cosx+c\] which somehow doesn't look right lol.

Answer 9

is not, maybe if you see the answer we can take a different approach... just a sec :)

Answer 10

\[(x^2+2x)sinx+(2x+2)cosx-2sinx+c\]

Answer 11

I got it :) it took triple integration by parts in one single problem @greenglasses

Answer 12

Oh my god. Well, at least it was all integration by parts- imagine if it were a bunch of different techniques mixed together.