Derivative with respect to a matrix in matrix multiplication I have this very simple problem, but I cannot seem to understand how this can be computed. I need to find the derivative with respect to a matrix that is part of matrix multiplication:
$$A_{(m,n)}*W_{(n,p)} = C_{(m,p)} \\ \frac{dC}{dW} = ?$$
I would need a matrix with the same dimensions as $W$ so $n$ by $p$, but whatever resources I find just confuse me more.. Is it not possible to express this in terms of $A$, the constant matrix? 

If $C(W) = AW$, then $C(W+H) = C(W) + AH$, so the derivative is $DC(W)(H) = AH$.
