本试题主要考查了双曲线的运用。
解:(1)设
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823213400735551.png)
的坐标分别为
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/201408232134007511102.png)
----------------1分
因为点M在双曲线C上,所以
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823213400766723.png)
,即
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823213400798507.png)
,所以
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823213400813682.png)
------2分
在
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823213400829743.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823213400860743.png)
中,
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823213400876802.png)
,
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823213400891687.png)
,所以
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823213400922726.png)
-------3分
由双曲线的定义可知:
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823213400938868.png)
故双曲线C的方程为:
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823213400688646.png)
-------------------4分
(2)①当切线l的斜率存在
设
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823213400985865.png)
,切线
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823213359862280.png)
的方程为:
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823213401032875.png)
代入双曲线C中,化简得:
所以
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/201408232134010632093.png)
-------------------6分
因为直线l与圆O相切,所以
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823213401094765.png)
,代入上式,得
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/201408232134011101298.png)
-----------7分
设点M的坐标为
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823213401125621.png)
,则
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/201408232134011562274.png)
所以-------------------8分
即|AB|=2|OM|成立
②当切线l的斜率不存在时,
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/201408232134016712396.png)
,
即|AB|=2|OM|成立-------------------10分
(3)由条件可知:两条渐近线分别为
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/201408232134016872465.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823213401702953.png)
------11分
设双曲线C上的点P(x
0,y
0),
则点P到两条渐近线的距离分别为
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/201408232134017182323.png)
--------------13分
因为P(x
0,y
0),在双曲线C:
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823213400688646.png)
上,所以
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823213401765640.png)
故
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/201408232134017801194.png)
-------------------14分
设
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/201408232134017962966.png)
-------------15分
-----16分