[偏微] 請教一題偏微題目

[bnm51315 (辛苦的耕耘)]

f(x,y)=c is joint probability density function with  x^2 + y^2 <= 1 and y>= 0
please find
(a) c and f(x,y) , f(x) , f(y)
(b) E(x,y)  ( ie. Expectation of xy ), E(x^2), E(y^2)
(c) E(x), E(y)


小弟不太懂其中提到的joint probability density function
還請各位先進指教  順便幫忙解一下這題的答案
麻煩囉 ^^

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→ Arthur4f:這是機率吧= ="?
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