formula

$f({\bf x}|{\bf \theta})=\displaystyle\frac{1}{2\pi^{n/2}\{\det(\Sigma)\}^{1/2}}\exp\left\{-\frac{1}{2}\ ^t({\bf x}-{\bf \mu})\Sigma^{-1}({\bf x}-{\bf \mu})\right\}$