Integrals! PLEASE HELP SOS

Question

anonymous · Answer

$$\int\limits xsin^2(x)$$

irishboy123 · Answer

sin^2 (x) is a pain.  so use a double angle formula and get it into cos(2x) c plus whatever.

from there, do it by parts, making sure you differentiate the x and integrate the trig function.

anonymous · Answer

how to get it into cos2s @IrishBoy123 ?

anonymous · Answer

cos2x

irishboy123 · Answer

the double angle formulae are your friend

in this case:

cos (2x) = cos^2 (x) - sin^2 (x) = 1 - 2 sin^2 (x)
so sin^2 (x) = (1/2) { 1 - cos (2x) }

you really need to know these working at the level you are at.  

then just multiply this into your integral and it will immediately look easier.    then just churn out the integration by parts.

anonymous · Answer

I got exemptions from last year, you're right, it's just been a while

anonymous · Answer

thanks allot!!!!

irishboy123 · Answer

you'll be back in the saddle in no time.  good luck!