如图,AB是⊙O的直径,AC是⊙O的切线,BC交⊙O于点E.
![](https://img.xkw.com/dksih/QBM/2016/4/19/1572597104369664/1572597110833152/STEM/3c3d5f0111da442e863aae870e774ef1.png)
(Ⅰ)若D为AC的中点,证明:DE是⊙O的切线;
(Ⅱ)若OA=
CE,求∠ACB的大小.
![](https://img.xkw.com/dksih/QBM/2016/4/19/1572597104369664/1572597110833152/STEM/3c3d5f0111da442e863aae870e774ef1.png)
(Ⅰ)若D为AC的中点,证明:DE是⊙O的切线;
(Ⅱ)若OA=
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a7ffe8515ff6183c1c7775dc6f94bdb8.png)
更新时间:2016-12-04 05:59:55
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【知识点】 几何证明选讲
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解答题-证明题
|
较易
(0.85)
【推荐1】如图,
的外接圆的切线AE与BC的延长线相交于点E,
的平分线与BC相交于点D,求证:
![](https://img.xkw.com/dksih/QBM/2016/1/20/1572453249368064/1572453255716864/STEM/1c990949ea9f4d19870e62e9ce880c5b.png)
(1)
;
(2)
.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/dd936a2405709574af0a73543d94ad9c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6062582a0a1679aa777451f25008411d.png)
![](https://img.xkw.com/dksih/QBM/2016/1/20/1572453249368064/1572453255716864/STEM/1c990949ea9f4d19870e62e9ce880c5b.png)
(1)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c5a5594708b3d94026c639aff4446b4b.png)
(2)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/966cf0715271c1191cd086f173f25e65.png)
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解答题-证明题
|
较易
(0.85)
【推荐2】已知圆
的方程为:
,直线的方程为
,点
在直线上,过点
作圆
的切线
,切点为
.
![](https://img.xkw.com/dksih/QBM/2014/3/28/1571585931689984/1571585937055744/STEM/33bca3e29e0c4b7f9d5131abd5ea9285.png)
(1)若
,求点
的坐标;
(2)若点
的坐标为
,过点
的直线与圆
交于
两点,当
时,求直线
的方程;
(3)求证:经过
(其中点
为圆
的圆心)三点的圆必经过定点,并求出所有定点的坐标.
![](https://img.xkw.com/dksih/QBM/2014/3/28/1571585931689984/1571585937055744/STEM/3d5032b8e16a48278074a9b13b8ea604.png)
![](https://img.xkw.com/dksih/QBM/2014/3/28/1571585931689984/1571585937055744/STEM/6abf4320c25a4066a7e2a24e538245ee.png)
![](https://img.xkw.com/dksih/QBM/2014/3/28/1571585931689984/1571585937055744/STEM/9d100565713a4563a2fd17c899a1607e.png)
![](https://img.xkw.com/dksih/QBM/2014/3/28/1571585931689984/1571585937055744/STEM/4c31d272157744d7be133a5531fb8d1f.png)
![](https://img.xkw.com/dksih/QBM/2014/3/28/1571585931689984/1571585937055744/STEM/4c31d272157744d7be133a5531fb8d1f.png)
![](https://img.xkw.com/dksih/QBM/2014/3/28/1571585931689984/1571585937055744/STEM/3d5032b8e16a48278074a9b13b8ea604.png)
![](https://img.xkw.com/dksih/QBM/2014/3/28/1571585931689984/1571585937055744/STEM/baabd968640d4c81a564d36fdafe7bb7.png)
![](https://img.xkw.com/dksih/QBM/2014/3/28/1571585931689984/1571585937055744/STEM/52b6d604ae434a779657ffd90d2bde4f.png)
![](https://img.xkw.com/dksih/QBM/2014/3/28/1571585931689984/1571585937055744/STEM/33bca3e29e0c4b7f9d5131abd5ea9285.png)
(1)若
![](https://img.xkw.com/dksih/QBM/2014/3/28/1571585931689984/1571585937055744/STEM/a04519a6852340caa2812a0efeb7725e.png)
![](https://img.xkw.com/dksih/QBM/2014/3/28/1571585931689984/1571585937055744/STEM/4c31d272157744d7be133a5531fb8d1f.png)
(2)若点
![](https://img.xkw.com/dksih/QBM/2014/3/28/1571585931689984/1571585937055744/STEM/4c31d272157744d7be133a5531fb8d1f.png)
![](https://img.xkw.com/dksih/QBM/2014/3/28/1571585931689984/1571585937055744/STEM/0845fad52439481babaf3375ad63f674.png)
![](https://img.xkw.com/dksih/QBM/2014/3/28/1571585931689984/1571585937055744/STEM/4c31d272157744d7be133a5531fb8d1f.png)
![](https://img.xkw.com/dksih/QBM/2014/3/28/1571585931689984/1571585937055744/STEM/3d5032b8e16a48278074a9b13b8ea604.png)
![](https://img.xkw.com/dksih/QBM/2014/3/28/1571585931689984/1571585937055744/STEM/984da381678a48959f776f3216d78b9f.png)
![](https://img.xkw.com/dksih/QBM/2014/3/28/1571585931689984/1571585937055744/STEM/69d161424141467b8315d21609279a9e.png)
![](https://img.xkw.com/dksih/QBM/2014/3/28/1571585931689984/1571585937055744/STEM/279b4101d173432fbb45f681faed7d73.png)
(3)求证:经过
![](https://img.xkw.com/dksih/QBM/2014/3/28/1571585931689984/1571585937055744/STEM/be2e2157747d4fe5b7d90b4757732f45.png)
![](https://img.xkw.com/dksih/QBM/2014/3/28/1571585931689984/1571585937055744/STEM/3d5032b8e16a48278074a9b13b8ea604.png)
![](https://img.xkw.com/dksih/QBM/2014/3/28/1571585931689984/1571585937055744/STEM/3d5032b8e16a48278074a9b13b8ea604.png)
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