题目内容
双曲线
的左、右焦点分别为
,点
在其右支上,且满足
,则
的值是( )
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823225246046564.png)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823225246062443.png)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/201408232252460771038.png)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823225246093923.png)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823225246124417.png)
A.![]() | B.![]() | C.4024 | D.4015 |
C
解:根据题意可知离心率为
,则|PnF1|="|"
+
xn|=
+
xn,
|Pn+1F2|="|"
-
xn+1|=
xn+1-
,
因为|Pn+1F2|=|PnF1|,所以xn+1=xn+2,又P1F2⊥F1F2,
所以x1=2,xn=2n,x2012=4024.选C
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823225246186344.png)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823225246186344.png)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823225246186344.png)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823225246186344.png)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823225246186344.png)
|Pn+1F2|="|"
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823225246186344.png)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823225246186344.png)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823225246186344.png)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823225246186344.png)
因为|Pn+1F2|=|PnF1|,所以xn+1=xn+2,又P1F2⊥F1F2,
所以x1=2,xn=2n,x2012=4024.选C
![](http://thumb.zyjl.cn/images/loading.gif)
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