Okay I solved it..
First delete my other post about prove xyz= a^3 + b ^3 , ive posted too much in it.
In that topic i asked Integrate xcsc^2 x partially. I meant for to ask it in new topic.
Anyway i solved it.
I rearanged d/dx(u/v) = (u'v - v'u)v^2 = 1/v * u' - u/v^2 * v'
when u integrate both sides and rearrange u get
[u/v^2 * v'] dx = [1/v * u' dx] - u/v
I used this for integrate csx^2 x
where v= sinx , u= 1/cosx
U get Integral of csc^2 x = -cotx
Haha : I realised i already knew that lol.
Then u Use Integration by parts normally for xcsc^2 x
So no need to integrate it. I've done it.