已知:如图,AB是⊙O的直径,BC是弦,OD⊥BC于点F,交⊙O于点D,连接AD、CD,∠E=∠ADC.
![](https://img.xkw.com/dksih/QBM/2012/2/23/1573344638255104/1573344679149568/STEM/9955324a6bb44434b6943a9dd53d2056.png?resizew=114)
(1)求证:BE是⊙O的切线;
(2)若BC=6,tanA =
,求⊙O的半径.
![](https://img.xkw.com/dksih/QBM/2012/2/23/1573344638255104/1573344679149568/STEM/9955324a6bb44434b6943a9dd53d2056.png?resizew=114)
(1)求证:BE是⊙O的切线;
(2)若BC=6,tanA =
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/bf31876698721a199c7c53c6b320aa86.png)
12-13九年级上·北京·期末 查看更多[3]
更新时间:2016-12-05 07:20:51
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解答题-证明题
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【推荐1】如图,已知
的直径
垂直于弦
于点E,过C点作
交
的延长线于点G,连接
并延长交
于点F,且
.
![](https://img.xkw.com/dksih/QBM/editorImg/2023/3/1/be69b30f-9965-49da-b0a4-e870963c49b6.png?resizew=145)
(1)试问:
是
的切线吗?说明理由;
(2)请证明:E是
的中点;
(3)若
,求
的长.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3d97cdc586744d208b6f69c9813af977.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f52a58fbaf4fea03567e88a9f0f6e37e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9d78abbad68bbbf12af10cd40ef4c353.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5917b07a22333ed23e3ccfe65f19db2e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f52a58fbaf4fea03567e88a9f0f6e37e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e5a122e25cf4eb9f03ffe5ec823bfc31.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/03902478df1a55bc99703210bccab910.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0b62ce0cbffa4758c7a0e6fb7ca4d24e.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2023/3/1/be69b30f-9965-49da-b0a4-e870963c49b6.png?resizew=145)
(1)试问:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/abf80148409afb32ced0b4f59f1ba709.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3d97cdc586744d208b6f69c9813af977.png)
(2)请证明:E是
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b90e0f35eda1a729fed485f83da5ea9d.png)
(3)若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/54275b7e571660d0a9e0370fbfe5050b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9d78abbad68bbbf12af10cd40ef4c353.png)
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【推荐2】如图,在破残的圆形残片上,弦AB的垂直平分线交弧AB于点C,交弦AB于点D,已知AB=8cm,CD=2cm.
![](https://img.xkw.com/dksih/QBM/2014/12/9/1573765608603648/1573765614092288/STEM/ccadf91c-2cf7-4864-90ec-1e5d138a3c8c.png)
(1)求作此残片所在的圆(尺规作图,不写作法,保留作图痕迹);
(2)求出(1)中所作圆的半径.
![](https://img.xkw.com/dksih/QBM/2014/12/9/1573765608603648/1573765614092288/STEM/ccadf91c-2cf7-4864-90ec-1e5d138a3c8c.png)
(1)求作此残片所在的圆(尺规作图,不写作法,保留作图痕迹);
(2)求出(1)中所作圆的半径.
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【推荐3】问题探究与应用实践
(一)问题探究:
如图(1),已知直线
与水平视线
互相垂直,
,
在
上,
在
上,∠ACB叫做“视角”,点
叫做“视点”,⊙
是过
,
,
三点的圆.当视点
在直线
上移动时,视角∠ACB的大小会发生改变,可以证明:当视点
恰是⊙
的切点时,视角
最大,此时观察
的效果最佳.当视角
最大时:分别以直线
,
为x轴和y轴建立平面直角坐标系,如图(2).
,点B的坐标为
,试求圆心M的坐标及
的值;
(2)如果此时点A,
的坐标分别为(0,a),(0,
),请求出视点
的坐标.(用a,
的代数式表示)
(二)应用实践:
应用上述结论,让我们解决如下问题:
(3)如图(3),
是广场上挂的一个大屏幕电视,直线
是水平视线,屏幕最高点A和最低点
到水平视线
的距离分别为8米和4米.小明在水平视线上观看电视节目,当他的视角最大时,视点(在水平视线
上)到直线
的距离约是多少?(结果保留一位小数,参考数据:
)
(一)问题探究:
如图(1),已知直线
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0f85fca60a11e1af2bf50138d0e3fe62.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/294f5ba74cdf695fc9a8a8e52f421328.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5963abe8f421bd99a2aaa94831a951e9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7f9e8449aad35c5d840a3395ea86df6d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0f85fca60a11e1af2bf50138d0e3fe62.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c5db41a1f31d6baee7c69990811edb9f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/294f5ba74cdf695fc9a8a8e52f421328.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c5db41a1f31d6baee7c69990811edb9f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ac047e91852b91af639feec23a9598b2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5963abe8f421bd99a2aaa94831a951e9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7f9e8449aad35c5d840a3395ea86df6d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c5db41a1f31d6baee7c69990811edb9f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c5db41a1f31d6baee7c69990811edb9f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/294f5ba74cdf695fc9a8a8e52f421328.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c5db41a1f31d6baee7c69990811edb9f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ac047e91852b91af639feec23a9598b2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8fabb884dc5f9609de491245463bbe9a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f52a58fbaf4fea03567e88a9f0f6e37e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8fabb884dc5f9609de491245463bbe9a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/294f5ba74cdf695fc9a8a8e52f421328.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0f85fca60a11e1af2bf50138d0e3fe62.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d42309b95f8046291ff8f4b0b0c2ef02.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e23a56cf8842e103cc36b562704c5649.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0e9245e94832c6f7b0d4bf834275b3fc.png)
(2)如果此时点A,
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7f9e8449aad35c5d840a3395ea86df6d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2c94bb12cee76221e13f9ef955b0aab1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c5db41a1f31d6baee7c69990811edb9f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2c94bb12cee76221e13f9ef955b0aab1.png)
(二)应用实践:
应用上述结论,让我们解决如下问题:
(3)如图(3),
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f52a58fbaf4fea03567e88a9f0f6e37e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4eedae8d316c76e3d0b451256de03fb9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7f9e8449aad35c5d840a3395ea86df6d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4eedae8d316c76e3d0b451256de03fb9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4eedae8d316c76e3d0b451256de03fb9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f52a58fbaf4fea03567e88a9f0f6e37e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/da4abf862cae1cf9f0ac90232c7275c3.png)
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【推荐1】图,已知△PDC是⊙O的内接三角形,CP=CD,若将△PCD绕点P顺时针旋转,当点C刚落在⊙O上的A处时,停止旋转,此时点D落在点B处.
(1) 求证:PB与⊙O相切;
(2)当PD=2
, ∠DPC=30°时,求⊙O的半径长.
(1) 求证:PB与⊙O相切;
(2)当PD=2
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5c3f8c3ba00c59e0634ed10fa85289de.png)
![](https://img.xkw.com/dksih/QBM/2012/3/12/1573354294460416/1573354330529792/STEM/c4e12f75a3eb4f7b9dac3061aa699115.png?resizew=178)
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【推荐2】如图,
是
的直径,
为
的弦,
,
与
的延长线交于点
,过
点的切线交
于点
.
![](https://img.xkw.com/dksih/QBM/2022/4/17/2966633693536256/2988397160226816/STEM/3d13073fa74a4227a87cd8227ae1422f.png?resizew=258)
(1)求证:
;
(2)若
,
,直接写出弧
的长.(结果保留
)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/03902478df1a55bc99703210bccab910.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3d97cdc586744d208b6f69c9813af977.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f52a58fbaf4fea03567e88a9f0f6e37e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3d97cdc586744d208b6f69c9813af977.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7fab5b7a2c91f41d76d727f92016248a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/abd13974aebe38eb2a1d744a01ea5aa5.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f52a58fbaf4fea03567e88a9f0f6e37e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/dad2a36927223bd70f426ba06aea4b45.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7f9e8449aad35c5d840a3395ea86df6d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/abd13974aebe38eb2a1d744a01ea5aa5.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c5db41a1f31d6baee7c69990811edb9f.png)
![](https://img.xkw.com/dksih/QBM/2022/4/17/2966633693536256/2988397160226816/STEM/3d13073fa74a4227a87cd8227ae1422f.png?resizew=258)
(1)求证:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4873d8ad1e20bcf10282395229e32b79.png)
(2)若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e73fdf9b92c4a65c9b72903da5bbc54b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a259656caff73f08304c865fe8f5205e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d40b319212a7e7528b053e1c7097e966.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/86ebba6ed1add0fe647c0226614b9290.png)
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