题目
题型:不详难度:来源:
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033650-42516.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033650-49610.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033650-30069.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033650-37276.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033650-91124.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033650-68667.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033650-61339.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033650-20642.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033650-41856.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033651-77953.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033651-15148.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033651-70081.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033651-70324.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033651-93052.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033651-50739.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033651-98913.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033651-86189.png)
(Ⅰ)求证:
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033651-93187.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033652-72979.png)
(Ⅱ)求直线
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033651-93187.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033652-66457.png)
答案
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033652-44165.png)
解析
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033652-76110.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033652-93909.png)
(2)可以采用空间向量法求解,求出平面
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033652-66457.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033652-91819.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033652-90114.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033652-91819.png)
(Ⅰ)证明:取
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033653-68761.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033653-66633.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033653-33678.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033653-33258.png)
因为
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033653-33738.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033653-62777.png)
所以
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033653-65774.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033654-73349.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033654-82847.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033654-93051.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033654-64473.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033654-51514.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033654-54391.png)
所以
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033654-75115.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033654-83371.png)
又二面角
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033654-83371.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033654-32345.png)
又因为
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033655-80264.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033655-53452.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033655-92669.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033655-53452.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033655-73317.png)
(Ⅱ)解:由(Ⅰ)可知
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033655-53452.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033655-73317.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033654-54391.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033650-30069.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033656-94192.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033656-91583.png)
则
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033656-59506.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033656-87379.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033657-64562.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033657-25964.png)
在图1中,连结
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033657-31544.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033657-40673.png)
所以
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033658-19873.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033653-68761.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033658-23364.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033658-30788.png)
所以
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033651-15148.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033657-31544.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033658-78634.png)
故点
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033650-91124.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033659-79997.png)
所以
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033659-54466.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033659-11893.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033659-13736.png)
不妨设平面
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033700-17244.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033700-67668.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033700-77086.png)
即
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033700-90091.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033701-60719.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033701-41559.png)
所以
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033701-41605.png)
故直线
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033701-15111.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033700-17244.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033652-44165.png)
核心考点
试题【如图1,在边长为的正三角形中,,,分别为,,上的点,且满足.将△沿折起到△的位置,使二面角成直二面角,连结,.(如图2) (Ⅰ)求证:⊥平面;(Ⅱ)求直线与平面】;主要考察你对向量与空间位置关系等知识点的理解。[详细]
举一反三
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033637-38589.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033638-93136.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033638-52447.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033638-74065.png)
A.若![]() ![]() ![]() |
B.若![]() ![]() ![]() |
C.若![]() ![]() ![]() ![]() |
D.若![]() ![]() ![]() ![]() |
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033620-66999.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033621-74627.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033621-28459.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033621-32788.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033621-52001.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033622-33676.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033622-59792.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033621-28459.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033622-64961.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033623-93116.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033623-28692.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033623-61754.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033621-52001.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033623-88596.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033623-74362.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033624-26365.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033624-61632.png)
(Ⅰ)当
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033624-71484.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033625-97277.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033625-99244.png)
(Ⅱ)若直线
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033625-26315.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033625-39462.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033626-61789.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033626-89884.png)
如图,已知
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033605-98244.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033605-63765.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033605-59551.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033605-90595.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033605-82153.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033606-73781.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033606-13240.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033606-29240.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033606-39642.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033606-10349.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033605-59551.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033606-49096.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033606-65212.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033606-87256.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033606-39642.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033607-24638.png)
(Ⅰ)求证:平面
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033607-17590.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033607-28926.png)
(Ⅱ)试确定点
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033606-87256.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033607-49661.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033608-62487.png)
(Ⅲ)当
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033606-87256.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033606-39642.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033608-80996.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033558-80217.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033558-73917.png)
①若
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033558-78680.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033559-85635.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033558-73917.png)
②若
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033559-50061.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033558-78680.png)
③若
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033559-85635.png)
如图,在四棱锥
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033548-49403.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033549-68263.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033549-75262.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033549-81964.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033549-51326.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033549-51922.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033549-98513.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033549-23269.png)
(Ⅰ)当E为侧棱SC的中点时,求证:SA∥平面BDE;
(Ⅱ)求证:平面BDE⊥平面SAC
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