(2003•天津)已知,如图⊙O
1与⊙O
2外切于点A,BC是⊙O
1和⊙O
2的公切线,B、C为切点.
(1)求证:AB⊥AC;
(2)若r
1、r
2分别为⊙O
1、⊙O
2的半径,且r
1=2r
2.求
![manfen5.com 满分网](http://img.manfen5.com/res/CZSX/web/STSource/20131021232441953884086/SYS201310212324419538840006_ST/0.png)
的值.
考点分析:
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