矩阵求导 向量求导 多元函数求导
$$
\begin{aligned}
&\bigtriangledown_A tr AB = B^T
\\ \ \ \\
&\bigtriangledown_A^T f(A) = [\bigtriangledown_A f(A)]^T
\\ \ \\
&\bigtriangledown_A trABA^TC = CAB+C^TAB^T
\\ \ \\
&\bigtriangledown_A |A| = |A|(A-1)^T
\end{aligned}
$$
$$
f(x) = x^Ax, x为n元向量
\\
\bigtriangle
