1 . 如图所示,已知
是圆心,直径
和弦
相交于点
,
,
,
,则
等于
![](https://img.xkw.com/dksih/QBM/2017/1/25/1619472216219648/1619472216457216/STEM/3921ec3c590445baa52a1041fd79ab28.png)
![](https://img.xkw.com/dksih/QBM/2017/1/25/1619472216219648/1619472216457216/STEM/d078ad3c5e304917969a5aa2637fb94a.png)
![](https://img.xkw.com/dksih/QBM/2017/1/25/1619472216219648/1619472216457216/STEM/46a3f5efc0014ce6bf83a536bc3d05d9.png)
![](https://img.xkw.com/dksih/QBM/2017/1/25/1619472216219648/1619472216457216/STEM/0265cd0807b94ce28d417b8cee9202cf.png)
![](https://img.xkw.com/dksih/QBM/2017/1/25/1619472216219648/1619472216457216/STEM/32b78dd824ba4c139fdec2dbcf656d84.png)
![](https://img.xkw.com/dksih/QBM/2017/1/25/1619472216219648/1619472216457216/STEM/13a221a800c94202b39b9ed179bda3bb.png)
![](https://img.xkw.com/dksih/QBM/2017/1/25/1619472216219648/1619472216457216/STEM/5a8ad33512354a158f701b6ec772fa42.png)
![](https://img.xkw.com/dksih/QBM/2017/1/25/1619472216219648/1619472216457216/STEM/532c4f12fc4c4f66904c9f31d9674345.png)
![](https://img.xkw.com/dksih/QBM/2017/1/25/1619472216219648/1619472216457216/STEM/46a3f5efc0014ce6bf83a536bc3d05d9.png)
![](https://img.xkw.com/dksih/QBM/2017/1/25/1619472216219648/1619472216457216/STEM/3921ec3c590445baa52a1041fd79ab28.png)
A.3 | B.8 |
C.12 | D.14 |
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真题
2 . 选修4-1:几何证明选讲
如图AB是
直径,AC是
切线,BC交
与点E.
![](https://img.xkw.com/dksih/QBM/2015/6/24/1572143053012992/1572143059132416/STEM/4728723fed18470d84dbc7e44107ef4f.png)
(Ⅰ)若D为AC中点,求证:DE是
切线;
(Ⅱ)若
,求
的大小.
如图AB是
![](https://img.xkw.com/dksih/QBM/2015/6/24/1572143053012992/1572143059132416/STEM/f611407c50d540ad9104c02c63aee4ba.png)
![](https://img.xkw.com/dksih/QBM/2015/6/24/1572143053012992/1572143059132416/STEM/f611407c50d540ad9104c02c63aee4ba.png)
![](https://img.xkw.com/dksih/QBM/2015/6/24/1572143053012992/1572143059132416/STEM/f611407c50d540ad9104c02c63aee4ba.png)
![](https://img.xkw.com/dksih/QBM/2015/6/24/1572143053012992/1572143059132416/STEM/4728723fed18470d84dbc7e44107ef4f.png)
(Ⅰ)若D为AC中点,求证:DE是
![](https://img.xkw.com/dksih/QBM/2015/6/24/1572143053012992/1572143059132416/STEM/f611407c50d540ad9104c02c63aee4ba.png)
(Ⅱ)若
![](https://img.xkw.com/dksih/QBM/2015/6/24/1572143053012992/1572143059132416/STEM/67dc69fe27884a1a8ff1aaa71bdd61c7.png)
![](https://img.xkw.com/dksih/QBM/2015/6/24/1572143053012992/1572143059132416/STEM/ce093531127143b1baddcccf84486568.png)
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3 . (几何证明选做题)如图,已知
内接于圆
,点
在
的延长线上,
切圆
于
,若
,
,则
的长为____________ .
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/15c0dbe3c080c4c4636c64803e5c1f76.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1dde8112e8eb968fd042418dd632759e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8455657dde27aabe6adb7b188e031c11.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/828628c0876b45381c9a0edeb0fec236.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/03902478df1a55bc99703210bccab910.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1dde8112e8eb968fd042418dd632759e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5963abe8f421bd99a2aaa94831a951e9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2fb01d2b57580731c8b807ac8cffc8ba.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7bb5b12692517a39c320f99a479eb055.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/03902478df1a55bc99703210bccab910.png)
![](https://img.xkw.com/dksih/QBM/2015/3/24/1572021911527424/1572021917130752/STEM/8d444bc8f9494355b491ed6c71cc4ff9.png?resizew=126)
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