如图,在平行四边形ABCD中,点E在边BC上,连结AE并延长,交对角线BD于点F、DC的延长线于点G.如果
,求
的值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9a3d1a4734b970ed363e8c2ad048469b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f48b4cd05033e0e57178ae777e9dcd03.png)
![](https://img.xkw.com/dksih/QBM/2020/3/19/2422690601697280/2423446156935168/STEM/bd9a8e994a55471aa32213f2af4e1bb4.png?resizew=144)
2020·湖北武汉·一模 查看更多[6]
2020年湖北省武汉市江夏区中考3月数学模拟试题(已下线)相似三角形模型湖北省武汉市江夏一中2019-2020学年九年级下学期第一期质量检测数学试题江西省九江市湖口县2022-2023学年九年级上学期期中数学试卷 (已下线)重难点08相似三角形基本模型(7种模型) -2022-2023学年九年级数学考试满分全攻略(人教版)青岛版九年级上册第1章图形的相似单元测试数学试题
更新时间:2020-03-20 08:56:44
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解答题-问答题
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【推荐1】如图,在平行四边形
中,
.点P在
上由点B向点C出发,速度为每秒
;点Q在边
上,同时由点D向点A运动,速度为每秒
.当点P运动到点C时,点P,Q同时停止运动.连接
,设运动时间为t秒.
(1)当t为何值时,四边形
为平行四边形?
(2)设四边形
的面积为y,求y与t之间的函数关系式.
(3)当t为何值时,四边形
的面积是四边形
的面积的四分之三?求出此时
的度数.
(4)连接
,是否存在某一时刻t,使
为等腰三角形?若存在,请求出此刻t的值;若不存在,请说明理由.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9c96b2cbc1310b0c53133c7bda26a3e9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0dc5c9827dfd0be5a9c85962d6ccbfb1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c78d0ab561d0c9bb9099772c596af8bf.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/03902478df1a55bc99703210bccab910.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/048b61a5fb5f420c6d7de88db5bc3aa5.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7a5f1641947153c80b987320885a2b57.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2023/7/2/49af83f0-797d-422e-91c7-6358d90b77eb.png?resizew=352)
(1)当t为何值时,四边形
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/712d9d9e29645c1df6ae23125b4aa1cc.png)
(2)设四边形
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/712d9d9e29645c1df6ae23125b4aa1cc.png)
(3)当t为何值时,四边形
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/712d9d9e29645c1df6ae23125b4aa1cc.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/72ddbaef2518ddf8b7a1e1e97faf74f4.png)
(4)连接
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/20a541b81584a032f571159ea152c85a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7a855335176fc36a15017f50a8561348.png)
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【推荐2】如图,已知△ABC中,AB=AC,将△ABC绕点A沿顺时针方向旋转得到△ADE,连接BD,CE交于点F.
![](https://img.xkw.com/dksih/QBM/editorImg/2022/9/29/2914f533-8fdf-4760-a92c-5f521496235e.png?resizew=161)
(1)求证:△AEC≌△ADB;
(2)若AB=1,∠BAC=45°,当四边形ADFC是平行四边形时,求EC的长.
![](https://img.xkw.com/dksih/QBM/editorImg/2022/9/29/2914f533-8fdf-4760-a92c-5f521496235e.png?resizew=161)
(1)求证:△AEC≌△ADB;
(2)若AB=1,∠BAC=45°,当四边形ADFC是平行四边形时,求EC的长.
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【推荐1】如图,AB是⊙O的直径,点C、E位于⊙O上AB两侧.在BA的延长线上取点D,使∠ACD=∠B.
(1)求证:DC是⊙O的切线;
(2)当BC=EC时,求证:AC2=AE•AD;
(3)在(2)的条件下,若BC=4
,AD:AE=5:9,求⊙O的半径.
(1)求证:DC是⊙O的切线;
(2)当BC=EC时,求证:AC2=AE•AD;
(3)在(2)的条件下,若BC=4
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2967337e3fcb228dded64ab0c41a17e0.png)
![](https://img.xkw.com/dksih/QBM/2020/7/3/2497707041103872/2497996183019520/STEM/b0cdb693cc9a433fadaa5a0971dfa670.png?resizew=178)
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【推荐2】如图,点
是
外一点,过点
作两条直线
,
,其中
是圆的切线,切点是
,过点
作弦![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b79dd200766db27fb90d6bd1992cf658.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2a9bfa68259d7a331be323b2038d628a.png)
,连接
交
于点
,直线
与直线
相交于点
.
,
,求证:![](https://staticzujuan.xkw.com/quesimg/Upload/formula/33fad71a947d49981a542f2e33a184dd.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f89eef3148f2d4d09379767b4af69132.png)
;
(2)若直线
为
的切线,切点为
,过点
作
的切线,交
于点
,已知![](https://staticzujuan.xkw.com/quesimg/Upload/formula/460c3a0db006e19ad307953dc8b0e233.png)
,求解
的长度.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/dad2a36927223bd70f426ba06aea4b45.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4f009e4f0098557f70667bfe8161c4da.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/dad2a36927223bd70f426ba06aea4b45.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/294f5ba74cdf695fc9a8a8e52f421328.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b6a24198bd04c29321ae5dc5a28fe421.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/5963abe8f421bd99a2aaa94831a951e9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b79dd200766db27fb90d6bd1992cf658.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2a9bfa68259d7a331be323b2038d628a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b6a24198bd04c29321ae5dc5a28fe421.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/30513ea48bc1ef3ae78adac83d894f14.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4f009e4f0098557f70667bfe8161c4da.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2a30f3a8b673cc28bd90c50cf1a35281.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b9f79d7939c88e9702962e5917cad290.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b6a24198bd04c29321ae5dc5a28fe421.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/cf3834d7ec7531f3c3c0ce9b286f7a49.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/07e37b122a7273e1251ea3860e74c896.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/89228eb0607106eca7e6d012c3cee9bb.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/33fad71a947d49981a542f2e33a184dd.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f89eef3148f2d4d09379767b4af69132.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a8f334f0800c00f02014dedcc61f2f0a.png)
(2)若直线
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b6a24198bd04c29321ae5dc5a28fe421.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4f009e4f0098557f70667bfe8161c4da.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c5db41a1f31d6baee7c69990811edb9f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7f9e8449aad35c5d840a3395ea86df6d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4f009e4f0098557f70667bfe8161c4da.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d4d260c4df7b0dc180af6980d21f3371.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a0ed1ec316bc54c37c4286c208f55667.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/460c3a0db006e19ad307953dc8b0e233.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/38387ba1cadfd3dfc4dea4ca9f613cea.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0cfa296598884a0dab43841422fa0b12.png)
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【推荐3】请阅读下列材料,并完成相应的任务.
在数学中,当问题的条件不够时间,常添加辅助线构成新图形,形成新关系,建立已知与未知的桥梁,从而把原问题转化为易于解决的问题.在著名美籍匈牙利数学教波利亚所著的《数学的发现》一书中有这样一个例子:试作一个三角形,使它的三边长分别是各条中线长的三分之一,解决这个问题的步骤如下:
![](https://img.xkw.com/dksih/QBM/2020/3/26/2427716980408320/2433472980795392/STEM/894e50037dfe438fbc3b00157545e8f3.png?resizew=105)
第一步,如图1,已知
的三条中线
,
和
相交于点
,则有
.
下面是该结论的部分证明过程:
![](https://img.xkw.com/dksih/QBM/2020/3/26/2427716980408320/2433472980795392/STEM/23d134a62ed44428a509147b13e4ce71.png?resizew=272)
证明:如图1,过点
作
的平分线,交
的延长线于点
,则
.
又
,
∴
.
∴
.
∵点
是
的中点,
∴
.
……
第二步,同理可以证明:
.
第三步,如图2,取BM的中点
,连接
.则
的三边长分别是各条中线长的三分之一.
任务:(1)请在上面第一步中证明过程的基础上完成对结论
的证明;
(2)请完成第三步的结论的证明;
(3)请直接写出图2中
与
的面积比:
_______.
在数学中,当问题的条件不够时间,常添加辅助线构成新图形,形成新关系,建立已知与未知的桥梁,从而把原问题转化为易于解决的问题.在著名美籍匈牙利数学教波利亚所著的《数学的发现》一书中有这样一个例子:试作一个三角形,使它的三边长分别是各条中线长的三分之一,解决这个问题的步骤如下:
![](https://img.xkw.com/dksih/QBM/2020/3/26/2427716980408320/2433472980795392/STEM/894e50037dfe438fbc3b00157545e8f3.png?resizew=105)
第一步,如图1,已知
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0faed94a64b2dcfc6801b4fca0f16675.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/03902478df1a55bc99703210bccab910.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/85c4bdfb0db1e31e8459df1d15f9ab55.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4cae70b8a9d2d2e96dea62c00ced04b9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ac047e91852b91af639feec23a9598b2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6a4cf8e2f179bbfc8fe2ca2ee5d61781.png)
下面是该结论的部分证明过程:
![](https://img.xkw.com/dksih/QBM/2020/3/26/2427716980408320/2433472980795392/STEM/23d134a62ed44428a509147b13e4ce71.png?resizew=272)
证明:如图1,过点
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c5db41a1f31d6baee7c69990811edb9f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/85c4bdfb0db1e31e8459df1d15f9ab55.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/03902478df1a55bc99703210bccab910.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/895dc3dc3a6606ff487a4c4863e18509.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/645ad3349dbd0e1a08b76fec95a7a039.png)
又
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8b945d94dd64621826240c31d603333d.png)
∴
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/73061cc06bb6a26b996d788fca0ceb42.png)
∴
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5b5ae2ff1a23ad5154d849d77266ff45.png)
∵点
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2a30f3a8b673cc28bd90c50cf1a35281.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/60ef95894ceebaf236170e8832dcf7e3.png)
∴
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4fd24e7934338068e33feba620137086.png)
……
第二步,同理可以证明:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/cf57f5df0062efbb4ff254c25fd54181.png)
第三步,如图2,取BM的中点
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/acc290b44635265137fdf13146b6a6d9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3525ddc5153fada64eaf14e50b536542.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/63454de6592b73da4da4a0a75cbe8d72.png)
任务:(1)请在上面第一步中证明过程的基础上完成对结论
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6a4cf8e2f179bbfc8fe2ca2ee5d61781.png)
(2)请完成第三步的结论的证明;
(3)请直接写出图2中
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/17bfa0ee19f0e9775103513e4fb21407.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0faed94a64b2dcfc6801b4fca0f16675.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c86ab5278a637256072178b05c7b0301.png)
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