In GMMs the probability density function of the mth component is given by:
\(p_{m}({\bf x}\vert \theta_{m})={1\over (2\pi)^{d/2}\vert \Sigma_{m}\vert ^{1/2}}\exp(-{1\over 2}({\bf x}-\mu_{m})^{T}\Sigma_{m}^{-1}({\bf x}-\mu_{m})),\eqno{\hbox{(2)}}\)
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