解题方法
1 . 设在平面内给定一个四边形
,
分别为
的中点,求证:
.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/42c2d86d8daea5e652d99fe1c6bc3f9a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f758a811b8a2c260431aa7e6a4060987.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/cabd34cc1dd98500753380a223d5f7c8.png)
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2 . 已知过点A(0,1)且斜率为
的直线
与圆C:
相交于M、N两点.
(1)求实数
的取值范围
(2)求证:
为定值
(3)若O为坐标原点,且
,求K值.
![](https://img.xkw.com/dksih/QBM/2015/2/4/1571975398850560/1571975404519424/STEM/b7efc9d0982e4ccc822471b573523742.png)
![](https://img.xkw.com/dksih/QBM/2015/2/4/1571975398850560/1571975404519424/STEM/bd8e8a69cd1b40818e460a3832c60e3b.png)
![](https://img.xkw.com/dksih/QBM/2015/2/4/1571975398850560/1571975404519424/STEM/13d64e25301b42a7baefd3f2d7d0fb6a.png)
(1)求实数
![](https://img.xkw.com/dksih/QBM/2015/2/4/1571975398850560/1571975404519424/STEM/b7efc9d0982e4ccc822471b573523742.png)
(2)求证:
![](https://img.xkw.com/dksih/QBM/2015/2/4/1571975398850560/1571975404519424/STEM/e4bc370fe1394756bd90048b0ab1e0df.png)
(3)若O为坐标原点,且
![](https://img.xkw.com/dksih/QBM/2015/2/4/1571975398850560/1571975404519424/STEM/b61380d6eff04ba8bbaf8a65ce4d01d6.png)
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