Now, consider joint density of $X, Y$ : $$ f_{X, Y}(x, y)=\left\{\begin{array}{l} \frac{1}{\pi} ; X^2+Y^2<1 \\ 0 ; \text { Otherwise } \end{array}\right. $$ Derive $E(Y \mid X)$.
I know how to calculate E(Y), but how do you calculate the conditional expectation? please help