条件期望的定义:条件期望公式[朗读]

f(x)f(y)=[e^x-e^-x][e^y-e^-y]=e^(x+y)-e^(x-y)-e^[-(x-y)]+e^[-(x+y)]=g(x+y)-g(x-y)=4g(x)g(y)=[e^x+e^-x][e^y+e^-y]=e^(x+y)+e^(x-y)+e^[-(x-y)]+e^[-(x+y)]=g(x+y)+g(x-y)=8解得:g(x+y)=6g(x-y)=2因此:g(x+y)/g(x-y)=3。