解题方法
1 . 已知抛物线C:
的准线为l,圆O:
.
(1)当
时,圆O与抛物线C和准线l分别交于点A,B和点M,N,且
,求抛物线C的方程;
(2)当
时,点
是(1)中所求抛物线C上的动点.过P作圆O的两条切线分别与抛物线C的准线l交于D,E两点,求
面积的最小值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/62c2f156b05838deaae6a35acad242af.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c3503d330608e7138d1b529aba4512fa.png)
(1)当
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/45767ebe3415761178db9b024da09b00.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/875d94138025df50536b04e8b0caa5cc.png)
(2)当
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7551011cfb75b26f35b07d6617c6a18b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3a79f5fb4d993e31ba286b57bd0ee53c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7cff7399ecc698e2fb415147c96d0d03.png)
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2 . 设点
在直线
上,
与
轴相切,且经过点
,则
的半径为 _____ .
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ac047e91852b91af639feec23a9598b2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0985b973395bcd371cd1e26d3fcd1c36.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3fef27cb7cb1b666c1734c65a7aa9aa4.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d053b14c8588eee2acbbe44fc37a6886.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d8b61bb7cb94b4d06f0090df1e365667.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3fef27cb7cb1b666c1734c65a7aa9aa4.png)
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