如图,⊙O与⊙O′相交于A和B,PQ切⊙O于P,交⊙O′于Q和M,交AB的延长线于N,MN=3,NQ=15,则PN=( )
![](http://img.shitiku.com.cn/uploads/allimg/20191108/20191108000827-16919.jpg) A.3 | B.![](http://img.shitiku.com.cn/uploads/allimg/20191108/20191108000827-87054.png) | C.3![](http://img.shitiku.com.cn/uploads/allimg/20191108/20191108000827-53217.png) | D.3![](http://img.shitiku.com.cn/uploads/allimg/20191108/20191108000828-59517.png) |
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举一反三
如图,AB为⊙O的直径,C为⊙O上一点,AP和过C的切线互相垂直,垂足为P,过B的切线交过C的切线于T,PB交⊙O于Q,若∠BTC=120°,AB=4,则PQ·PB=( )
![](http://img.shitiku.com.cn/uploads/allimg/20191108/20191108000821-73069.jpg) A.2 | B.3 | C.![](http://img.shitiku.com.cn/uploads/allimg/20191108/20191108000821-86999.png) | D.2![](http://img.shitiku.com.cn/uploads/allimg/20191108/20191108000821-86999.png) |
| 两个相似三角形,面积分别为16cm2和49cm2,它们的周长相差6cm,则较大三角形的周长为( )A.21cm | B.2cm | C.14cm | D. cm |
| 如图是某高速公路一个隧道的横截面,若它的形状是以O为圆心的圆的一部分,路面AB=10m,净高CD=7m,则此圆的半径OA=________m.
![](http://img.shitiku.com.cn/uploads/allimg/20191108/20191108000813-64779.jpg) | 如图,AB是半圆O的直径,C是半圆O上异于A,B的点,CD⊥AB,垂足为D,已知AD=2,CB=4 ,则CD=________.
![](http://img.shitiku.com.cn/uploads/allimg/20191108/20191108000810-30475.jpg) | 如图,已知PA与⊙O相切,A为切点,PBC为割线,D为⊙O上一点,AD、BC相交于点E.
![](http://img.shitiku.com.cn/uploads/allimg/20191108/20191108000805-19153.jpg) (1)若AD=AC,求证:AP∥CD; (2)若F为CE上一点使得∠EDF=∠P,已知EF=1,EB=2,PB=4,求PA的长. |
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