Test
\( \sum\limits_{k = 1}^n {{k^2} = \frac{{n(n + 1)(2n + 1)}}{6}} \)
\(\Delta = \left|\begin{array}{cc} 10 & 0 & 0 \\ \mathrm{\cos}\alpha & \mathrm{\sin}\alpha & - 6 \\ \mathrm{\cos}\beta & \mathrm{\sin}\beta & - 6 \\ \end{array}\right|\)
[ 本帖最後由 Lopez 於 2023-4-25 13:31 編輯 ]
