题目内容
如图,直线y=m与抛物线y2=4x交于点A,与圆(x-1)2+y2=4的实线部分交于点B,F为抛物线的焦点,则三角形ABF的周长的取值范围是 ( )
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824035738654870.png)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824035738654870.png)
A.(2,4) | B.(4,6) | C.[2,4] | D.[4,6] |
B
试题分析:因为圆(x-1)2+y2=4的圆心坐标为(1,0),与抛物线y2=4x的焦点重合,所以
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824035738669469.png)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824035738685597.png)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824035738700624.png)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/201408240357387161213.png)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824035738732516.png)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140824/20140824035738732539.png)
![](http://thumb.zyjl.cn/images/loading.gif)
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题目内容
A.(2,4) | B.(4,6) | C.[2,4] | D.[4,6] |