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[几何] 立体几何（正方形，折起）

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lrh2006 Posted 2016-4-11 15:31 |Read mode

求帮助，多谢！

QQ图片20160411153009.png

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血狼王 Posted 2016-4-11 18:45

答案是$$\frac{2}{\sqrt{5}}.$$
提示：
证明$$A'E\perp CD.$$

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Author| lrh2006 Posted 2016-4-11 23:04

回复 2# 血狼王

谢谢，答案对的，为什么A'E⊥CD，还请再指点一下

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Author| lrh2006 Posted 2016-4-12 09:14

回复 2# 血狼王

噢，我明白了，是这样的，多谢啦

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nkzxwdy Posted 2016-4-12 09:20

取CD中点F,连结A'F,EF,可证得A′E⊥CD.

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Author| lrh2006 Posted 2016-4-12 09:48

回复 5# nkzxwdy

嗯嗯，明白了，谢谢你

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血狼王 Posted 2016-4-14 04:50

回复 4# lrh2006

不用谢，我是雷锋

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游客 Posted 2016-4-14 15:18

要是对图形没什么感觉的话，直接用坐标去算，就是工作量大点，不怎么用动脑筋也不难算。

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Author| lrh2006 Posted 2016-4-15 13:17

回复 8# 游客

好的，谢谢

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