题目
题型:不详难度:来源:
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022083213-56637.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022083213-56637.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022083214-80046.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022083213-56637.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022083214-38720.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022083214-12727.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022083213-56637.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022083214-22443.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022083215-68725.gif)
求证:(1)
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022083215-62631.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022083215-25526.gif)
(2)平面
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022083215-69464.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022083214-12727.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022083215-25526.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022083215-69533.gif)
答案
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022083216-50087.gif)
∵
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022083214-80046.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022083216-15268.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022083214-22443.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022083215-68725.gif)
∴
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022083215-62631.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022083216-50087.gif)
又∵
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022083215-62631.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022083216-71331.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022083215-25526.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022083216-91588.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022083215-25526.gif)
∴
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022083215-62631.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022083215-25526.gif)
(Ⅱ)∵
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022083214-38720.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022083214-12727.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022083213-56637.gif)
∴
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022083214-38720.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022083214-12727.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022083217-59597.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022083217-35987.gif)
又∵
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022083216-15268.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022083214-12727.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022083217-59597.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022083216-15268.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022083217-59260.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022083214-38720.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022083214-80046.gif)
∴
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022083217-59597.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022083214-12727.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022083215-69464.gif)
而
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022083217-59597.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022083217-78878.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022083215-25526.gif)
∴平面
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022083215-69464.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022083214-12727.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022083215-25526.gif)
解析
核心考点
举一反三
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022083159-56878.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022083159-98627.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022083200-54788.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022083200-69039.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022083200-93646.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022083200-12967.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022083201-92692.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022083201-97876.jpg)
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![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022083201-51442.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022083201-68242.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022083201-51442.gif)
![]() |
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![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022083202-21206.gif)
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![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022083202-69541.gif)
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![]() |
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已知在四棱锥P-ABCD中,底面ABCD是边长为4的正方形,△PAD是正三角形,平面PAD⊥平面ABCD,E、F、G分别是PA、PB、BC的中点.
(1)求证:EF
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022083148-10916.gif)
(2)求平面EFG与平面ABCD所成锐二面角的大小;
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022083149-89951.jpg)
如图7,在直三棱柱
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022083109-99739.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022083109-63997.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022083109-71081.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022083109-54813.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022083110-62573.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022083110-25826.gif)
(1)求证:
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022083110-21720.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022083110-29423.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022083110-34639.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022083110-24050.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022083102-96631.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022083102-22259.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022083102-11042.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022083102-96631.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022083103-61297.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022083103-92651.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022083102-96631.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191022/20191022083103-34063.gif)
A.![]() | B.![]() | C.![]() | D.![]() |
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