[iSimon]

So yeah I'm doing a bit of late night revision (because I'm suddenly panicking at how close exams are and how little revision I've done...) and I got stuck on this question and I was wondering if anyone could help?

It's to integrate this
2sin3xsin2x

I tried to do it by parts...but failed....
(the answer in the mark scheme is sinx - 1/5sin5x + c )
I appreciate you reading

[Glutamic Acid]

Product-to-sum identities.

[Necro Defain]

Integration by parts twice

[rnd]

Use this identity..

[maths-enthusiast]

cos (3x+2x)=?
cos (3x-2x)=?
This may help

[iSimon]

wow never seen that identity before but it worked! :o

Thank you all

I'm gonna have to go look more up about it now :P

[nuodai]

They're infinitely useful, and the fact that they don't seem to appear in many A-level syllabuses disturbs me:
http://www.mathwords.com/p/product_t...identities.htm
http://www.mathwords.com/s/sum_to_pr...identities.htm