立体几何一题

realnumber · 2015-1-26 10:25

realnumber · 2015-1-26 10:28

Last edited by realnumber 2015-1-26 10:351.$2\sqrt{2}$
2.设BC中点M,AD中点N,
那么有O到AD距离小于等于$\abs{OM}+\abs{MN}$
可得取等时，最大，此时BN在面α上射影长度为$2\sqrt{3}\cos{(∠NBC-45\du)}=2+\sqrt{2}$，AD射影长度为4,所以面积为$4+2\sqrt{2}$

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[几何] 立体几何一题

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