We know that so we just need to calculate . Let , for . Then put
Now we have
Not sure why it hates my teXing... anyways its solved
Haven't used this for a while.. not sure if i get the texing.
I prove first that (this was fine)
Then i am to calculate, assuming all the have finite fourth moment, denoting , the
. I first used and tried to calculate but
I don't really get how these cross terms work. My first attempt i got but i'm only assuming that's wrong.