题目内容
如图,已知圆O1与圆O2相交于A,B两点,直线O1A交圆O1于C,交圆O2于D,连接CB
![精英家教网](http://thumb.1010pic.com/pic2/upload/papers/20130926/201309260621089279678.png)
并延长交圆O2于E,AF切圆O1于A,交CE于F.
(1)求证:
=
;
(2)若
=
,圆O1的半径为2,且∠C=30°,求DE的长.
![精英家教网](http://thumb.1010pic.com/pic2/upload/papers/20130926/201309260621089279678.png)
并延长交圆O2于E,AF切圆O1于A,交CE于F.
(1)求证:
CA |
CD |
AF |
DE |
(2)若
CA |
AD |
3 |
2 |
![精英家教网](http://thumb.1010pic.com/pic2/upload/papers/20130926/2013092606210892711158.png)
(1)证明:连接AB.
∵AC是直径,
∴∠CBA=90°.
又∵四边形ABED内接于⊙O2,
∴∠CBA=∠D=90°.
又∵AF切⊙O1于A点,
∴∠CAF=90°.
∴AF∥DE.
∴
CA |
CD |
AF |
DE |
(2)∵
CA |
AD |
3 |
2 |
又∵CA=1,
∴CD=
20 |
3 |
在Rt△CDE中,tan30°=
DE | ||
|
∴DE=
20 |
9 |
3 |
![](http://thumb2018.1010pic.com/images/loading.gif)
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