题目
题型:不详难度:来源:
正方体
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021025745-70665.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021025745-38694.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021025746-97022.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021025746-94595.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021025746-92069.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021025746-89243.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021025746-58888.gif)
(Ⅰ)求证:直线
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021025747-95343.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021025747-73739.gif)
(Ⅱ)求证:
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021025747-90125.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021025747-83153.gif)
(Ⅲ)求三棱锥
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021025748-37571.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021025748-23894.gif)
答案
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021025748-76674.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021025748-81260.gif)
∵
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021025746-89243.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021025746-58888.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021025746-97022.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021025746-92069.gif)
∴
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021025748-76674.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021025747-95343.gif)
又∵
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021025748-48310.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021025747-73739.gif)
∴直线
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021025747-95343.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021025747-73739.gif)
(Ⅱ)在正方体
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021025745-70665.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021025749-81890.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021025749-37873.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021025749-84332.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021025749-37873.gif)
∴
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021025749-48560.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021025750-97691.gif)
且
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021025750-56215.gif)
∴
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021025750-95438.gif)
∴
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021025750-50817.gif)
同理可证
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021025750-75235.gif)
∵
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021025751-38604.gif)
∴
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021025747-90125.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021025747-83153.gif)
(Ⅲ)
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021025751-82096.gif)
解析
核心考点
试题【(本小题共14分)正方体的棱长为,是与的交点,为的中点.(Ⅰ)求证:直线∥平面;(Ⅱ)求证:平面;(Ⅲ)求三棱锥的体积.】;主要考察你对空间几何体的结构特征等知识点的理解。[详细]
举一反三
如图,已知直三棱柱ABC—A1B1C1,
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021025736-22959.gif)
(1)求证:
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021025736-82727.gif)
(2)求四棱锥A—ECBB1的体积;
(3)判断直线CF和平面AEB1的位置关系,并加
以证明。
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021025736-60679.gif)
如图,在底面是正方形的四棱锥P—ABCD中,PA⊥面ABCD,BD交AC于点E,F是PC中点,G为AC上一点.
(I)求证:BD⊥FG;
(II)确定点G在线段AC上的位置,使FG//平面PBD,并说明理由.
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021025727-29513.jpg)
三棱柱
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021025719-22416.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021025719-35586.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021025719-96582.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021025719-65921.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021025719-15649.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021025719-60021.gif)
(Ⅰ)求证:
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021025719-13153.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021025719-95477.gif)
(Ⅱ)求证:
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021025720-40962.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021025720-50541.gif)
(Ⅲ)求三棱锥
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021025720-29801.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021025720-50541.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021025720-79654.gif)
三棱柱ABC—A1B1C1的每条棱长均为4,E、F分别是BC,A1C1
的中点,则EF的长等于 。
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021025700-31331.jpg)
如图,四棱锥P—ABCD中,
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021025647-27470.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021025648-39815.gif)
(Ⅰ)求证:
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021025648-55608.gif)
(Ⅱ)点M在AD边上,若PA//平面MEG,
求
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021025648-60184.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191021/20191021025648-44643.jpg)
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