Whats a quick way to work the below (and problems similar) out?

For me to take this derivative it involves a lot of time and boring calculation, there has to be a better way.

This is taken from the solutions to Chris Bishop's Pattern Recognition and Machine learning:

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#### Best Answer

There is something called the Matrix Cookbook, which includes a lot of identities and matrix derivatives. So if we look at eq. (88) of the Matrix Cookbook,

$$frac{partial}{partial A} (mathbf{x} -mathbf{A}mathbf{s})^Tmathbf{W}(mathbf{x} -mathbf{A}mathbf{s}) = -2mathbf{W}(mathbf{x}-mathbf{A}mathbf{s})mathbf{s}^T$$

we see that this directly refers to your problem, if we assume $Sigma^{-1}$ is a covariance matrix and therefore symmetric.

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