190412-CSDN寫博客時多行公式對齊

https://ask.csdn.net/questions/701470

$$
\begin{aligned}
u \cdot n
& =u n^T \\
& = u(A A^{-1})n^T \\
& =(uA)(A^{-1}n^T) \\
& =(uA)((A^{-1}n^T)^T)^T \\
& =(uA)(n(A^{-1})^T)^T \\
& =uA \cdot n(A^{-1})^T \\
& =uA\cdot nB \\
& =0
\end{aligned}
$$

$\begin{aligned} u \cdot n & =u n^T \\ & = u(A A^{-1})n^T \\ & =(uA)(A^{-1}n^T) \\ & =(uA)((A^{-1}n^T)^T)^T \\ & =(uA)(n(A^{-1})^T)^T \\ & =uA \cdot n(A^{-1})^T \\ & =uA\cdot nB \\ & =0 \end{aligned}$