
Re: [理工] 機率-隨機變數轉換

: 用變數代換法都會變成機率總和為二
: Why?
u = x + y
v = -x + y
∞
f_U(u) = ∫f_xy(x(u ,v), y(u, v)) * (1/2) dv
-∞
∞
= ∫f_xy(u, v) * (1/2) dv
-∞
當u < 1:
u
f_U(u) = ∫ (1/2) dv = u
-u
當u > 1:
2-u
f_U(u) = ∫ (1/2) dv = (1/2)[4 - 2u] = 2 - u
u-2
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