How to simplify certain covariance expressions using

*To*: mathgroup at smc.vnet.net*Subject*: [mg128027] How to simplify certain covariance expressions using*From*: hewei2004 at gmail.com*Date*: Sun, 9 Sep 2012 17:33:24 -0400 (EDT)*Delivered-to*: l-mathgroup@mail-archive0.wolfram.com*Delivered-to*: l-mathgroup@wolfram.com*Delivered-to*: mathgroup-newout@smc.vnet.net*Delivered-to*: mathgroup-newsend@smc.vnet.net

Hi, I have a certain case of covariance to simplify. Suppose I have the following expression: cov=(ea+ex)(ea+ey)=eaea+eaex+eaey+exey How can I assume that whenever ex times ey ,the product is 0, so that the expression I want to get out of is Assuming[exey=0,Refine[cov]]=eaea+eaex+eaey So that the last term:exey, drops out. My problem is that the Assuming[] function won't take exey=0 as a valid assumption. Is there any way to do this using some other function or I typed something wrong?

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**Re: How to simplify certain covariance expressions using***From:*Bob Hanlon <hanlonr357@gmail.com>

**Re: How to simplify certain covariance expressions using***From:*Barrie Stokes <Barrie.Stokes@newcastle.edu.au>

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