(A derivation of the bivariate normal distribution) let $Z_{1}$ and
$Z_{2}$ be independent n(0,1) random variables, and define new
random variables X and Y by\\
\begin{align*}
X=a_{x}Z_{1}+b_{x}Z_{2}+c_{x} \quad
Y=a_{Y}Z_{1}+b_{Y}Z_{2}+c_{Y}\\
\end{align*}
where $a_{x},b_{x},c_{x},a_{Y},b_{Y},c_{Y}$ are constants.\\
if we define the constants $a_{x},b_{x},c_{x},a_{Y},b_{Y},c_{Y}$
by\\
\begin{align*}
a_{x}=\sqrt{\frac{1+\rho}{2}}\sigma_{X},
b_{x}=\sqrt{\frac{1-\rho}{2}}\sigma_{X}, c_{X}=\mu_{X},\\
a_{Y}=\sqrt{\frac{1+\rho}{2}}\sigma_{Y},
b_{Y}=-\sqrt{\frac{1-\rho}{2}}\sigma_{Y},c_{Y}=\mu_{Y}\\
\end{align*}
where \mu_{X}, \mu_{Y},\sigma^2_{x},\sigma^2_{Y},\rho are
constants\\
\\
\begin{itemize}
\item
Question 1):\\
Show that $(X,Y)$ has the bivariate normal pdf with parameter\\s
$\mu_{X}, \mu_{Y},\sigma^2_{x},\sigma^2_{Y},\rho$\\
\item
Question 2):\\
if we start with bivariate normal parameters...