题目
题型:不详难度:来源:
![](http://img.shitiku.com.cn/uploads/allimg/20191023/20191023045053-16816.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191023/20191023045053-97539.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191023/20191023045054-29702.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191023/20191023045054-39002.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191023/20191023045054-96114.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191023/20191023045054-79452.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191023/20191023045053-97539.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191023/20191023045055-13883.png)
A.![]() | B.![]() |
C.![]() | D.![]() |
![](http://img.shitiku.com.cn/uploads/allimg/20191023/20191023045056-39320.png)
答案
解析
![](http://img.shitiku.com.cn/uploads/allimg/20191023/20191023045056-84557.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191023/20191023045056-74783.png)
解答:解:∵在△ABC中,AB=5,BC=3,CA=4∴△ABC是直角三角形
∵O是△ABC的外心∴OC=
![](http://img.shitiku.com.cn/uploads/allimg/20191023/20191023045056-67411.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191023/20191023045057-22644.png)
∴cos∠OCA=cos∠OAC=
![](http://img.shitiku.com.cn/uploads/allimg/20191023/20191023045057-89155.png)
设
![](http://img.shitiku.com.cn/uploads/allimg/20191023/20191023045056-84557.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191023/20191023045056-74783.png)
cosθ=cos(π-∠OCA)=-cos∠OCA=-
![](http://img.shitiku.com.cn/uploads/allimg/20191023/20191023045057-89155.png)
∴
![](http://img.shitiku.com.cn/uploads/allimg/20191023/20191023045057-25494.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191023/20191023045056-84557.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191023/20191023045056-74783.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191023/20191023045056-67411.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191023/20191023045057-89155.png)
故选D.
核心考点
举一反三
如图
![](http://img.shitiku.com.cn/uploads/allimg/20191023/20191023045041-96813.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191023/20191023045042-58426.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191023/20191023045042-35522.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191023/20191023045042-14757.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191023/20191023045042-58426.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191023/20191023045042-78975.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191023/20191023045042-40487.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191023/20191023045043-83479.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191023/20191023045043-33960.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191023/20191023045044-77552.gif)
平面
![](http://img.shitiku.com.cn/uploads/allimg/20191023/20191023045044-35012.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191023/20191023045044-69035.gif)
(Ⅰ)求异面直线
![](http://img.shitiku.com.cn/uploads/allimg/20191023/20191023045044-59345.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191023/20191023045042-58426.gif)
(Ⅱ)证明
![](http://img.shitiku.com.cn/uploads/allimg/20191023/20191023045045-65838.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191023/20191023045045-73972.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191023/20191023045045-81740.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191023/20191023045035-14817.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191023/20191023045035-56423.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191023/20191023045035-94667.png)
A、
![](http://img.shitiku.com.cn/uploads/allimg/20191023/20191023045036-68579.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191023/20191023045036-86427.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191023/20191023045036-44861.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191023/20191023045036-97356.png)
已知
![](http://img.shitiku.com.cn/uploads/allimg/20191023/20191023045029-94874.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191023/20191023045029-44703.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191023/20191023045029-44703.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191023/20191023045029-56006.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191023/20191023045029-86032.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191023/20191023045029-44703.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191023/20191023045029-83083.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191023/20191023045030-69225.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191023/20191023045030-33660.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191023/20191023045024-14736.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191023/20191023045025-63744.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191023/20191023045025-75844.gif)
A.![]() | B.![]() | C.![]() | D.![]() |
![](http://img.shitiku.com.cn/uploads/allimg/20191023/20191023045013-44970.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191023/20191023045013-65616.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191023/20191023045013-73233.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191023/20191023045014-77177.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191023/20191023045014-69128.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191023/20191023045014-15449.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191023/20191023045014-33047.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191023/20191023045014-67697.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191023/20191023045015-12030.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191023/20191023045015-45847.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191023/20191023045014-33047.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191023/20191023045013-73233.gif)
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