如图1,在边长为
的等边∆
中,点
是边
上一个动点,过点
作
⊥
于点
.
(1)求证:
;
(2)如图2,过点
向
引垂线交
于点
,当
时,试判断
点在
上的位置,并说明理由;
(3)如图3,延长
至
,使
,连接
交
于点
,随着
点的移动,请判断线段
的长度是否发生变化;若变化,请说明理由;若不变,请求出
的值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6f8c4c029e552954bd493b49aeab82d5.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7bef5239ddbb0972700ce01daf9ee7cf.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8455657dde27aabe6adb7b188e031c11.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/e6e490f703eb6c9bb1278c78ebc2d661.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/60ef95894ceebaf236170e8832dcf7e3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2a30f3a8b673cc28bd90c50cf1a35281.png)
(1)求证:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/74101ac8be711374f0e4ff8aa750bb51.png)
(2)如图2,过点
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8455657dde27aabe6adb7b188e031c11.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0dc5c9827dfd0be5a9c85962d6ccbfb1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0dc5c9827dfd0be5a9c85962d6ccbfb1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a0ed1ec316bc54c37c4286c208f55667.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7faabc484ce3666706c1beffda4bcfe2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8455657dde27aabe6adb7b188e031c11.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f52a58fbaf4fea03567e88a9f0f6e37e.png)
(3)如图3,延长
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0dc5c9827dfd0be5a9c85962d6ccbfb1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/895dc3dc3a6606ff487a4c4863e18509.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/963e0391a2b071c0f81cff5920c8598d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1e72b2e1ff83e95df048745322982451.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/60ef95894ceebaf236170e8832dcf7e3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/73465a1f9aa03481295bf6bd3c6903ac.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8455657dde27aabe6adb7b188e031c11.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/589786dd7c3a2679c3230b671cd232d6.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/589786dd7c3a2679c3230b671cd232d6.png)
![](https://img.xkw.com/dksih/QBM/2021/7/7/2758999685087232/2822896043507712/STEM/4833cfee-086e-4554-97b5-bd38aa619edd.png)
20-21八年级上·湖南长沙·期末 查看更多[3]
湖南省长沙市宁乡市2020-2021学年八年级上学期期末数学试题(已下线)【期末测试】综合能力提升卷(考试范围:第十一~十五章)-【冲刺高分】2021-2022学年八年级数学上册培优拔高必刷卷(人教版)(已下线)第08讲 等腰三角形(7大考点)-2022-2023学年八年级数学考试满分全攻略(人教版)
更新时间:2021-10-05 17:39:36
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解答题-证明题
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【推荐1】《几何原本》是一部集前人思想和欧几里得个人创造性于一体的不朽之作,它建立了一套从公理、定义出发,论证命题得到定理的几何学论证方法,形成了一个严密的逻辑体系﹣﹣﹣几何学.以下是《几何原本》第一卷中的命题6,请完成它的证明过程.
命题6:如果一个三角形有两个角相等,那么这两个角所对的边也相等.
已知: .
求证: .
证明:若AB≠AC,其中必有一个较大,不妨设AB>AC,在AB上截取BD=AC,
连接DC.
∵ ,
,
,
∴△ACB≌△DBC
∴∠BDC=∠CAB .
又∠BDC>∠CAB .
∴∠BDC与∠CAB即等于又大于,显然是矛盾的.
∴假设不成立,即AB=AC.
命题6:如果一个三角形有两个角相等,那么这两个角所对的边也相等.
已知: .
求证: .
证明:若AB≠AC,其中必有一个较大,不妨设AB>AC,在AB上截取BD=AC,
连接DC.
∵ ,
,
,
∴△ACB≌△DBC
∴∠BDC=∠CAB .
又∠BDC>∠CAB .
∴∠BDC与∠CAB即等于又大于,显然是矛盾的.
∴假设不成立,即AB=AC.
![](https://img.xkw.com/dksih/QBM/2020/1/10/2373828932681728/2374124089802752/STEM/45eb28826b1742b8a533c534c5c93cca.png?resizew=137)
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解答题-问答题
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【推荐2】如图,在
中,
,
,点
是
边上一点,
(
),作点
关于直线
的对称点
,连接
交
于点
.连接
并延长交直线
于点
,连接BE、AD.
![](https://img.xkw.com/dksih/QBM/editorImg/2023/1/13/d5f17053-4fdd-47d7-bb55-f99b03efdf4f.png?resizew=162)
(1)当
时,
______;
(2)嘉琪说:“无需给出
的具体数值,也可求出
的值,”请运用相关知识验证嘉琪的说法是否正确.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/15c0dbe3c080c4c4636c64803e5c1f76.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/047dc9795efa99b6fb9fdf9778085dab.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/456e0f77d83975fdbdb60b499cb5b521.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/dad2a36927223bd70f426ba06aea4b45.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0dc5c9827dfd0be5a9c85962d6ccbfb1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e5c9d96d2dc0082bb375c3b0e7214bdf.png)
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(1)当
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(2)嘉琪说:“无需给出
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![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1a55a1a244f81097e05e715b69580faa.png)
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【推荐1】在
中,
,
,
,点
,
分别在
,
上,沿
将
翻折,使顶点
的对应点
落在
边上,若
,求
的长.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/15c0dbe3c080c4c4636c64803e5c1f76.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/60d9142db4dd2ef151bf3d4a63afb61e.png)
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【推荐2】如图,为测量广场雕塑的高度AB,小明在广场平地上的点C处,测得雕塑顶部A的仰角为
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.
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(1)若D到CA的距离为 m;
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(1)若D到CA的距离为 m;
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【推荐1】如图,已知
,点
,
在边
上,连接
,
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.
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解答题-问答题
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【推荐2】如图,在菱形
中,
,E,F分别是边
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与
之间的数量关系为______;
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(3)若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/145f13fd586e0bdbda15f25b576c6c83.png)
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