解答题-证明题 较易0.85 引用1 组卷326
如图,在三棱锥
中,
,
,点
为
中点,
是
上一点,
底面
,
面
.
![](https://img.xkw.com/dksih/QBM/2017/2/8/1625057959280640/1625057959772160/STEM/8b409250e8284a5b99560171eebe8698.png)
(1)求证:
为
中点;
(2)当
取何值时,
在平面
内的射影恰好是
的中点.
![](https://img.xkw.com/dksih/QBM/2017/2/8/1625057959280640/1625057959772160/STEM/c29870433a19470293a67a7bab07feb0.png)
![](https://img.xkw.com/dksih/QBM/2017/2/8/1625057959280640/1625057959772160/STEM/eb7e37a162654bb681e7ac2c40659068.png)
![](https://img.xkw.com/dksih/QBM/2017/2/8/1625057959280640/1625057959772160/STEM/8497f833a51d4476b9511611643c4a03.png)
![](https://img.xkw.com/dksih/QBM/2017/2/8/1625057959280640/1625057959772160/STEM/703a66f358b640bfa6af53f70e8d11e5.png)
![](https://img.xkw.com/dksih/QBM/2017/2/8/1625057959280640/1625057959772160/STEM/026a735903f343abb14b76be22b259cd.png)
![](https://img.xkw.com/dksih/QBM/2017/2/8/1625057959280640/1625057959772160/STEM/44e39aa6328944b49bde881f0cb68af3.png)
![](https://img.xkw.com/dksih/QBM/2017/2/8/1625057959280640/1625057959772160/STEM/312a1c381f784ef3a3d9859171a4156b.png)
![](https://img.xkw.com/dksih/QBM/2017/2/8/1625057959280640/1625057959772160/STEM/54008c53b0ab4cba9be1bb06464c7e81.png)
![](https://img.xkw.com/dksih/QBM/2017/2/8/1625057959280640/1625057959772160/STEM/c71c4a530c7344e0b0fdb6af356e3fcf.png)
![](https://img.xkw.com/dksih/QBM/2017/2/8/1625057959280640/1625057959772160/STEM/6d29b9cee3754af69ec7bce10f1ae57c.png)
![](https://img.xkw.com/dksih/QBM/2017/2/8/1625057959280640/1625057959772160/STEM/52ae8e3d5c7845fdb76152fd3d3dc8c9.png)
![](https://img.xkw.com/dksih/QBM/2017/2/8/1625057959280640/1625057959772160/STEM/8b409250e8284a5b99560171eebe8698.png)
(1)求证:
![](https://img.xkw.com/dksih/QBM/2017/2/8/1625057959280640/1625057959772160/STEM/44e39aa6328944b49bde881f0cb68af3.png)
![](https://img.xkw.com/dksih/QBM/2017/2/8/1625057959280640/1625057959772160/STEM/312a1c381f784ef3a3d9859171a4156b.png)
(2)当
![](https://img.xkw.com/dksih/QBM/2017/2/8/1625057959280640/1625057959772160/STEM/854b331455bd481d89bc37ad7d6f1a84.png)
![](https://img.xkw.com/dksih/QBM/2017/2/8/1625057959280640/1625057959772160/STEM/703a66f358b640bfa6af53f70e8d11e5.png)
![](https://img.xkw.com/dksih/QBM/2017/2/8/1625057959280640/1625057959772160/STEM/6a86a48c8bed4f2894580529b3d1795d.png)
![](https://img.xkw.com/dksih/QBM/2017/2/8/1625057959280640/1625057959772160/STEM/33b39b962eea48c7b2c79ba0cddc64c8.png)
16-17高三·湖南长沙·阶段练习
类题推荐
组卷网是一个信息分享及获取的平台,不能确保所有知识产权权属清晰,如您发现相关试题侵犯您的合法权益,请联系组卷网
组卷网是一个信息分享及获取的平台,不能确保所有知识产权权属清晰,如您发现相关试题侵犯您的合法权益,请联系组卷网