Hi everybody,

I currently try to solve a problem that ends up with the question "What 
is the product of two normal distributions?". Unfortunately, I found 
nothing useful so far.

Now here is my problem:

I have two normally distributed variables X and Y. These variables are 
not independent.

The covariance cov(X,Y) = E(XY) - E(X)*E(Y) is not zero.

What I would like to know is: How does the covariance change, if I add a 
normally distributed variable Z (with Mu_Z = 0, Sigma_Z != 0) to Y?


Can I calculate cov(X,Y+Z) based on cov(X,Y) and Sigma_Z ?


Since E(Y + Z) = E(Y), all I would need is some clou on how E(X*(Y+Z)) 
looks like. But unfortunately, I don't know so far how X*(Y+Z) looks like.

I am thankful for any help!

Stefan

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