$x, a$ in $\mathbb R^n$, $A$ in $\mathbb R^{n\times n}$. I'm trying to compute $d(x^T A x)/dx$.
I got, in the last step: (x^T A)^T + Ax. Somebody said that this should equal 2Ax. Why is that?
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In general, $(AB)^T = B^TA^T$. So, you have $(x^TA)^T = A^Tx$ which in the special case of $A$ being symmetric, would simplify as suggested above. – JMoravitz Feb 20 '16 at 23:13
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I'm voting to close this question as off-topic because it appears to have been resolved (as per the newly added final line of post). – JMoravitz Feb 20 '16 at 23:14