题目
题型:不详难度:来源:
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105041226-53859.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105041226-76716.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105041226-43700.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105041227-20716.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105041227-39255.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105041227-75110.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105041227-73132.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105041228-26562.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105041228-29734.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105041227-39255.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105041228-56582.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105041228-68605.png)
小题1:求证:直线
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105041229-11846.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105041227-20716.png)
小题2:若
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105041229-79528.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105041229-57232.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105041227-75110.png)
答案
小题1:证明:连结AE. ∵ AB是圆O的直径,
∴ ÐAEB=90°.∴Ð1+Ð2=90°.………………………… 1分
∵ AB="AC," ∴ Ð1=
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105041229-96944.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105041229-96944.png)
∴ Ð1=ÐCBF,∴ ÐCBF+Ð2=90°.……………………… 4分
∵ 即ÐABF=90°.∵ AB是圆O的直径,
∴ 直线BF是圆O的切线; ……………………… 6分
小题2:∵ sinÐCBF=
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105041230-50147.png)
∴ sinÐ1=
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105041230-50147.png)
∵ ÐAEB=90°,AB="5," ∴BE=AB·sinÐ1=
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105041230-48064.png)
∵ AB=AC,ÐAEB=90°, ∴ BC=2BE=2
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105041230-48064.png)
解析
(2)利用三角函数求解
核心考点
举一反三
A.180 | B.270 | C.150 | D.200 |
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105041221-80259.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105041218-86947.png)
A.20° | B.30° | C.40° | D.35° |
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105041215-20279.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105041202-19344.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105041203-86724.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105041203-94028.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105041203-88562.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105041203-18348.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105041203-72289.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105041203-50405.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105041203-90858.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105041203-90858.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105041204-22559.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105041204-62589.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105041204-14314.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105041204-95915.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105041204-14314.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105041204-12288.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105041203-90858.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105041204-15813.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105041204-48039.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105041204-40748.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105041205-19481.png)
(1) 求证:
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105041205-38405.png)
(2)如图1,若
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105041205-62032.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105041205-44830.png)
(3) 如图2,设
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105041205-81008.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105041205-92902.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105041205-66097.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105041205-66097.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191105/20191105041206-38501.png)
A.![]() | B.1 | C.2 | D.![]() |
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