题目
题型:不详难度:来源:
![](http://img.shitiku.com.cn/uploads/allimg/20191102/20191102235136-59800.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191102/20191102235137-54584.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191102/20191102235137-76177.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191102/20191102235137-80960.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191102/20191102235137-37568.png)
答案
![](http://img.shitiku.com.cn/uploads/allimg/20191102/20191102235137-90626.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191102/20191102235138-19206.png)
解析
分析:由△ABC中,∠C为直角,CD⊥AB,根据等角的余角相等,即可求得∠BCD=∠A,又由BC=3,AB=5,利用勾股定理即可求得AC的长,然后在Rt△BCD中,利用三角函数的知识即可求得答案.
解:∵CD⊥AB,
∴∠CDB=90°,
∴∠B+∠BCD=90°,
∵△ABC中,∠C为直角,
∴∠A+∠B=90°,
∴∠A=∠BCD,
∵BC=3,AB=5,
∴AC=
![](http://img.shitiku.com.cn/uploads/allimg/20191102/20191102235138-26756.png)
在Rt△BCD中,DB=BC?sin∠BCD=BC?sin∠A=3×
![](http://img.shitiku.com.cn/uploads/allimg/20191102/20191102235138-64530.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191102/20191102235138-21066.png)
CD=BC?cos∠BCD=BC?cos∠A=3×
![](http://img.shitiku.com.cn/uploads/allimg/20191102/20191102235139-39504.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191102/20191102235139-48672.png)
故答案为:
![](http://img.shitiku.com.cn/uploads/allimg/20191102/20191102235138-21066.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191102/20191102235139-48672.png)
核心考点
举一反三
![](http://img.shitiku.com.cn/uploads/allimg/20191102/20191102235132-55843.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191102/20191102235132-66218.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191102/20191102235133-94415.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191102/20191102235124-37387.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191102/20191102235119-22199.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191102/20191102235119-84893.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191102/20191102235119-83117.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191102/20191102235119-56222.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191102/20191102235119-83117.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191102/20191102235120-28721.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191102/20191102235119-83117.png)
或 时,使得由点
![](http://img.shitiku.com.cn/uploads/allimg/20191102/20191102235120-15705.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191102/20191102235120-59312.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191102/20191102235120-54809.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191102/20191102235115-27653.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191102/20191102235108-78005.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191102/20191102235108-85841.png)
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