Answer

问题及解答

平行六面体的体积不大于由其中有公共顶点的三条边互相垂直时生成的方体的体积.

Posted by haifeng on 2012-07-26 09:40:17 last update 2012-07-26 10:19:02 | Edit | Answers (0)

证明:

\[
\begin{vmatrix}
x_1 & y_1 & z_1\\
x_2 & y_2 & z_2\\
x_3 & y_3 & z_3
\end{vmatrix}^2\leqslant(x_1^2+x_2^2+x_3^2)(y_1^2+y_2^2+y_3^2)(z_1^2+z_2^2+z_3^2).
\]