题目
题型:不详难度:来源:
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033300-72904.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033300-63435.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033301-17204.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033301-89125.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033301-23667.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033301-72720.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033302-26015.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033302-41401.jpg)
(I)证明:
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033302-90805.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033301-17204.png)
(II)求直线
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033302-90790.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033303-78000.png)
(III)在
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033303-36695.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033303-59672.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033303-20120.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033303-78000.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033303-59672.png)
答案
(II)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033304-82612.png)
(III) 存在这样的点E,E为
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033304-89393.png)
解析
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033300-63435.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033301-17204.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033304-11490.png)
(2)可以以O为原点,ON,OC,OA1所在直线为x,y,z轴建立空间直角坐标系,然后用向量的方法求解线面角的问题.
(3)在(2)的基础上也可以用向量来求点E位置.也可以取BC的中点M,连接OM,取BC1的中点E,连接ME,则OM//AB,ME//BB1//AA1,所以平面OMB//平面AA1B,所以OE//平面
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033303-78000.png)
(Ⅰ)证明:因为
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033304-61111.png)
所以
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033305-98020.png)
又由题意可知,平面
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033305-28397.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033305-19010.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033305-10189.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033305-13060.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033306-89989.png)
所以
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033306-30520.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033305-19010.png)
(Ⅱ)如图,以O为原点,
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033306-82870.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033307-69627.png)
由题意可知,
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033307-99445.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033307-36376.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033307-41550.png)
所以得:
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033307-26571.png)
则有:
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033308-99280.png)
设平面
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033308-94986.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033308-33776.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033308-88406.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033309-18654.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033309-96496.png)
所以
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033309-14421.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033309-50055.png)
因为直线
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033310-87301.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033310-95211.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033310-28056.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033310-23997.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033311-54884.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033304-82612.png)
(Ⅲ)设
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033311-38177.png)
即
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033311-96610.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033311-44277.png)
所以
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033311-39667.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033312-57722.png)
令
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033312-42298.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033310-95211.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033312-58065.png)
即
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033312-66732.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033313-42488.png)
即存在这样的点E,E为
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033304-89393.png)
核心考点
试题【(本题满分12分)如图,在三棱柱中,侧面底面,,,且为中点.(I)证明:平面;(II)求直线与平面所成角的正弦值;(III)在上是否存在一点,使得平面,若不存在】;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/20191106/20191106033253-60069.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033253-47303.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033253-89966.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033254-98614.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033254-52068.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033254-63728.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033254-30873.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033254-19038.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033255-61285.png)
(1) 证明:
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033255-20668.png)
(2) 证明:
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033255-15159.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033255-99696.png)
(3) 求二面角
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033256-37674.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033256-26161.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033242-72873.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033242-98616.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033242-68763.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033243-93881.png)
①
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033243-25893.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033243-97782.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033244-87712.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033244-54778.png)
A.②④ | B.①② | C.③④ | D.①③ |
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033228-83026.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033228-42661.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033229-23023.png)
(Ⅰ)求证:平面
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033229-97437.png)
(Ⅱ)当
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033229-24394.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033229-79708.png)
A.48 | B.18 | C.24 | D.36 |
将两块三角板按图甲方式拼好,其中
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033213-75919.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033214-32299.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033214-82802.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033214-74145.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033215-75751.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033215-60968.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033215-59068.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033215-71297.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033216-90743.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033216-81576.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033216-68814.png)
(Ⅰ)求证:
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033217-38812.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033217-66222.png)
(Ⅱ)求二面角
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106033217-28565.png)
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