旧知温习:人教版初中数学第二十七章《相似》中比例线段的证明都是利用三角形相似或平行线得出来的,在三角形相似证明中,利用的条件有角相等,对应边成比例.比例线段还可以写成等积式,如
可以写为
.
新知探究:如图1,
中,
是两条相交的弦,交点为P,(不再添加辅助线),求证:
;
类比探究:如图2,P是
外一点,
是
的两条割线,与
交点分别为A,B,C,D.请写出
的等积关系式,并说明理由.
延伸结论:如图2,
中,点P是
外一点,
是
的切线,切点为
是过圆心O的一条割线,交
于A和B点,请直接写出探究
之间的数量关系.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3e73309616b493938633c6182a584ace.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3845adc546277f54fec47ffec22792f6.png)
新知探究:如图1,
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3d97cdc586744d208b6f69c9813af977.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f9b79c80cc81b5446dfac3ee97b03c03.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1a5f6255503de9bcc36f483093b366e2.png)
类比探究:如图2,P是
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3d97cdc586744d208b6f69c9813af977.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/55002681d78a04b00998087b789f7879.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3d97cdc586744d208b6f69c9813af977.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3d97cdc586744d208b6f69c9813af977.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/fd6e75d1cecef29cbf097e6cc7e6ac7f.png)
延伸结论:如图2,
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3d97cdc586744d208b6f69c9813af977.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3d97cdc586744d208b6f69c9813af977.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/48f3c9abbd78e9a6840ee5f30381daac.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3d97cdc586744d208b6f69c9813af977.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/77197cb26423f929e8a57dc6f6daa15a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3d97cdc586744d208b6f69c9813af977.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7f38574d39a4c86ad000bf8ac63080da.png)
更新时间:2024-04-24 10:08:00
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【推荐1】如图,AB是⊙O的直径,OC是半径,延长OC至点D.连接AD,AC,BC.使∠CAD=∠B.
(1)求证:AD是⊙O的切线;
(2)若AD=4,tan∠CAD=
,求BC的长.
(1)求证:AD是⊙O的切线;
(2)若AD=4,tan∠CAD=
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f89eef3148f2d4d09379767b4af69132.png)
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【推荐2】问题提出:
如图1:在
中,
且
,点O为
的外心,则
的外接圆半径是 .
问题探究:
如图2,正方形
中,E、F分别是边
两边上点且
,请问线段
有怎样的数量关系?并说明理由.
问题解决:
如图3,四边形
中,
,
,点E、F分别是射线
上的动点,并且
,试问
的面积是否存在最小值?若存在,请求出最小值.若不存在,请说明理由.
如图1:在
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/15c0dbe3c080c4c4636c64803e5c1f76.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/57ebb33adb2310a6e03918761e68204a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3f81e24376a13d648c2ed0dc73bc710e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/15c0dbe3c080c4c4636c64803e5c1f76.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/15c0dbe3c080c4c4636c64803e5c1f76.png)
问题探究:
如图2,正方形
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a20cb2c77ea29b6eabbc477bc3743859.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/192155e6a3aade305b76b1eb7c75e30c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/172a5167d675937845d7c885c84a164c.png)
问题解决:
如图3,四边形
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9e6129f9f1fbb9334a10b4dc6c89aebc.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/062ba20f514cedda559d70ed78c5ac41.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3da188037fa76ddbcc3218e6086855f0.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/250f5d2a092b865eed16ac3ee98f8783.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4c105d6ba18fbb0581fb982175e2eac9.png)
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【推荐3】请阅读材料,并完成相应的任务.
任务:
(1)将探索小组的解题过程补充完整;
(2)如图3,当点P在
内时,![](https://staticzujuan.xkw.com/quesimg/Upload/formula/cb686e4f5e3938575bc547e849d5513f.png)
所对的一个圆内角,延长AP交
于点C,延长BP交
于点D,若设
,
所对的圆心角为n°,则∠APB的度数为______.
在数学探究课上,同学们发现改变图1中圆周角![]() ![]() ![]() ![]() ![]() ![]() 如图2,点A,B在 ![]() ![]() ![]() ![]() ![]() ![]() ![]() 探索小组的解题过程(部分)如下: 解:如图2,连接AD,OC,OD. ∵ ![]() ![]() ![]() ∴ ![]() … ![]() |
(1)将探索小组的解题过程补充完整;
(2)如图3,当点P在
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3d97cdc586744d208b6f69c9813af977.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/cb686e4f5e3938575bc547e849d5513f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/16d65cecaf8a3dc2953f4109c75a981e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3d97cdc586744d208b6f69c9813af977.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3d97cdc586744d208b6f69c9813af977.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/bff73892a5566e1eff4955174277e24d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83bb3820bab977db734f4335e4fde720.png)
![](https://img.xkw.com/dksih/QBM/2022/4/29/2968741691064320/2973750106120192/STEM/9d1f3a34-90e2-415d-86cc-a82e0c4b193e.png?resizew=172)
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【推荐1】为弘扬民族传统体育文化,某校将传统游戏“滚铁环”列入了校运动会的比赛项目.滚铁环器材由铁环和推杆组成.小明对滚铁环的启动阶段进行了研究,如图,滚铁环时,铁环
与水平地面相切于点C,推杆
与铅垂线
的夹角为
点O,A,B,C,D在同一平面内.当推杆
与铁环
相切于点B时,手上的力量通过切点B传递到铁环上,会有较好的启动效果.
.
(2)实践中发现,切点B只有在铁环上一定区域内时,才能保证铁环平稳启动.图中点B是该区域内最低位置,此时点A距地面的距离
最小,测得
.已知铁环
的半径为
,推杆
的长为
,求此时
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/03902478df1a55bc99703210bccab910.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/70fef891ad9c552f2e55f871e856ff32.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/996342924367c5da427f83a891951fb7.png)
(2)实践中发现,切点B只有在铁环上一定区域内时,才能保证铁环平稳启动.图中点B是该区域内最低位置,此时点A距地面的距离
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/03902478df1a55bc99703210bccab910.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f945a69cf7e8213e50622125cde652f5.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3d97cdc586744d208b6f69c9813af977.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3668a3f3ce5b8a272ad92c2ebd233f5a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f52a58fbaf4fea03567e88a9f0f6e37e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a3d8789e1f6656c346853f226c08863e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/03902478df1a55bc99703210bccab910.png)
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【推荐2】如图,Rt△ABC中,∠BAC=90°,E是AC的中点,AE=2.经过点E作△ABE外接圆的切线交BC于点D,过点C作CF⊥BC交BE的延长线于点F,连接FD交AC于点H,FD平分∠BFC.
![](https://img.xkw.com/dksih/QBM/2019/5/6/2197753082445824/2198724980531200/STEM/585488df6e2d4b8488a1a594c2cb407d.png?resizew=201)
(1)求证:DE=DC;
(2)求证:HE=HC=1;
(3)求BD的长度.
![](https://img.xkw.com/dksih/QBM/2019/5/6/2197753082445824/2198724980531200/STEM/585488df6e2d4b8488a1a594c2cb407d.png?resizew=201)
(1)求证:DE=DC;
(2)求证:HE=HC=1;
(3)求BD的长度.
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【推荐1】如图,四边形
是
的内接四边形,连接
,延长
至点
.
![](https://img.xkw.com/dksih/QBM/editorImg/2023/5/13/aa6bbbb7-c360-4c5a-9798-6f069902134b.png?resizew=171)
(1)若
,求证:
;
(2)若
,⊙O的半径为2,求
.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3d97cdc586744d208b6f69c9813af977.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/989c75a3fd02e4971cab421c88de92f1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9d78abbad68bbbf12af10cd40ef4c353.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2a30f3a8b673cc28bd90c50cf1a35281.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2023/5/13/aa6bbbb7-c360-4c5a-9798-6f069902134b.png?resizew=171)
(1)若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/047dc9795efa99b6fb9fdf9778085dab.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4e10ff2bca7cf0566a16ea0826926066.png)
(2)若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3f8eeeea1c9652cacce976f8129cf520.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a5cb63aeea0b37799404c8fec092b21d.png)
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【推荐2】如图,
是半圆的直径,
,
是半圆上的两点,且
的度数为
,
,求
的度数.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f52a58fbaf4fea03567e88a9f0f6e37e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c5db41a1f31d6baee7c69990811edb9f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8455657dde27aabe6adb7b188e031c11.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ed41d321f4c0717ac5b443aad942d9a7.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0aee6e4e9350a2665df8597ff8045bbd.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6ea0d1d36ccbf5c6e4513dae86c4228a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/727ad3e630a224303d6d3b8ad5c114ba.png)
![](https://img.xkw.com/dksih/QBM/2019/12/9/2351474877808640/2352368602128384/STEM/ed7f0b61508a426bb178add0d226d452.png?resizew=162)
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【推荐1】如图,已知
内接于
,
是直径,点
在
上,
,过点
作
,垂足为
,连接
交
边于点
.
(1)求证:
;
(2)求证:
;
(3)连接
,设
的面积为
,
,求四边形
的面积(用含有
的式子表示).
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/15c0dbe3c080c4c4636c64803e5c1f76.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/8455657dde27aabe6adb7b188e031c11.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3d97cdc586744d208b6f69c9813af977.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/063e06b7ede7ab41bab600aeb7e47ea7.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8455657dde27aabe6adb7b188e031c11.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/32c38dfd14dde969702dff97ef2270f9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2a30f3a8b673cc28bd90c50cf1a35281.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9d78abbad68bbbf12af10cd40ef4c353.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e6e490f703eb6c9bb1278c78ebc2d661.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a0ed1ec316bc54c37c4286c208f55667.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2023/11/17/b6a52b04-af1f-4760-8769-ab38629dac8e.png?resizew=146)
(1)求证:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/09cedf303362eff43f9309238caef693.png)
(2)求证:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/78bdb1cfd168f0efe605b6a13116d234.png)
(3)连接
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/828628c0876b45381c9a0edeb0fec236.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/74625390340982140e449e07663579a2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/cf231f8f86fb922df4ca0c87f044cec3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/953682eaa7294b153ff70cd5fb496e7e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/293b63e275caa57bae8c0f5a98c1a312.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/cf231f8f86fb922df4ca0c87f044cec3.png)
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【推荐2】如图,已知正方形ABCD中,BE平分∠DBC且交CD边于点E,将△BCE绕点C顺时针旋转到△DCF的位置,并延长BE交DF于点G
(1)求证:△BDG∽△DEG;
(2)若EG•BG=4,求BE的长.
![](https://img.xkw.com/dksih/QBM/editorImg/2023/11/28/836d8ce5-f36c-42db-9aa7-42e029f05a87.png?resizew=160)
(1)求证:△BDG∽△DEG;
(2)若EG•BG=4,求BE的长.
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