问题背景:如图1,在四边形
中,
,
,
,
,
,
绕B点旋转,它的两边分别交
、
于E、F.探究图中线段
之间的数量关系.小李同学探究此问题的方法是:延长
到G,使
,连接
,先证明
,再证明
,可得出结论,他的结论就是______________;
探究延伸:如图2,在四边形
中,
,
,
,
绕B点旋转,它的两边分别交
、
于E、F.上述结论是否仍然成立?并说明理由.
实际应用:如图3,在某次军事演习中,舰艇甲在指挥中心(O处)北偏西30°的A处舰艇乙在指挥中心南偏东70°的B处,并且两舰艇到指挥中心的距离相等接到行动指令后,舰艇甲向正东方向以75海里/小时的速度前进,同时舰艇乙沿北偏东50°的方向以100海里/小时的速度前进,1.2小时后,指挥中心观测到甲、乙两舰艇分别到达E、F处,且指挥中心观测两舰艇视线之间的夹角为70°,试求此时两舰艇之间的距离.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/97e45b6f8cf0260912f587c04f9f2442.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4e320a45fdb0f3339eff27dd0c608117.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2b6e4a2df58a236c20df5df0d29a466c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/645d46c17903078e0b38279353c5430d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2b432c0a8f179c78503d2e48e382eee6.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e44d9f2b82b73e7a0917a19f74dbc5f9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/03902478df1a55bc99703210bccab910.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9e52a8f07834cbbbe4224962672fbbb2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6e045bc50398f2a1196c67a83a1b00b5.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/735056c174e8dd7906257a2a50a962a7.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/82c4f440b65c520d479378fa89c1d375.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/06e322e0c87479bba874db9ae9ba36b5.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/85e666dd62dfcf04a01f00a073989646.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e06edc5c667d86bea8347a3ff9683017.png)
探究延伸:如图2,在四边形
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2b6e4a2df58a236c20df5df0d29a466c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/60e9cb665a4a1ddc999f8d03381f9f3e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7bd52c2dfe29fdc18c65e1f488f138bb.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e44d9f2b82b73e7a0917a19f74dbc5f9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/03902478df1a55bc99703210bccab910.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9e52a8f07834cbbbe4224962672fbbb2.png)
实际应用:如图3,在某次军事演习中,舰艇甲在指挥中心(O处)北偏西30°的A处舰艇乙在指挥中心南偏东70°的B处,并且两舰艇到指挥中心的距离相等接到行动指令后,舰艇甲向正东方向以75海里/小时的速度前进,同时舰艇乙沿北偏东50°的方向以100海里/小时的速度前进,1.2小时后,指挥中心观测到甲、乙两舰艇分别到达E、F处,且指挥中心观测两舰艇视线之间的夹角为70°,试求此时两舰艇之间的距离.
![](https://img.xkw.com/dksih/QBM/editorImg/2023/12/13/f0b6fd3d-46a0-48ca-9913-64cecf097c2e.png?resizew=475)
20-21八年级上·江西南昌·阶段练习 查看更多[4]
(已下线)【南昌新东方】2020年育华学校八年级10月份月考试卷 69江西省南昌市东湖区江西育华学校2020-2021学年八年级月考数学试题(已下线)12.1+全等三角形(题型精讲精练)-【题型分类精粹】2023-2024学年八年级数学上学期期中期末复习讲练系列3【考点闯关】(人教版)(已下线)23.2(培优课)半角模型(题型精讲精练)1(原卷版)
更新时间:2020-11-03 12:06:09
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解答题-证明题
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【推荐1】如图1,在
ABCD中,AE⊥BC于E,E恰为BC的中点,tanB=2.
![](https://img.xkw.com/dksih/QBM/editorImg/2022/9/2/4f0c3bbb-21ab-4ffe-a07f-10b4cd8d10df.png?resizew=322)
(1)求证:AD=AE;
(2)如图2,点P在BE上,作EF⊥DP于点F,连结AF,求证:DF-EF=
AF;
(3)请你在图3中画图探究:当P为射线EC上任意一点(P不与点E重合)时,作EF⊥DP于点F,连结AF,线段DF、EF与AF之间有怎样的数量关系?直接写出你的结论为____________.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/81a5328919a7cec382c2e91c9c528fc1.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2022/9/2/4f0c3bbb-21ab-4ffe-a07f-10b4cd8d10df.png?resizew=322)
(1)求证:AD=AE;
(2)如图2,点P在BE上,作EF⊥DP于点F,连结AF,求证:DF-EF=
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/cf298f00799cbf34b4db26f5f63af92f.png)
(3)请你在图3中画图探究:当P为射线EC上任意一点(P不与点E重合)时,作EF⊥DP于点F,连结AF,线段DF、EF与AF之间有怎样的数量关系?直接写出你的结论为____________.
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【推荐2】数学实践活动,是一种非常有效的学习方式.通过活动可以激发我们的学习兴趣,提高动手动脑能力,拓展思推空间,丰富数学体验.让我们一起动手来折一折、转一转、剪一剪,体会活动带给我们的乐趣.
折一折:将正方形纸片ABCD折叠,使边AB、AD都落在对角线AC上,展开得折痕AM、AN,连接MN,如图1.
![](https://img.xkw.com/dksih/QBM/2022/5/11/2977161474228224/2987925623463936/STEM/5d66f6f3-e38a-4ada-83b1-4842af752919.png?resizew=635)
(1)∠MAN=______
,写出图中两个等腰三角形:_________(不需要添加字母);
(2)转一转:将图1中的∠MAN绕点A旋转,使它的两边分别交边BC、CD于点E、F,连接EF,如图2.线段BE、EF、DF之间的数量关系为_________;
(3)连接正方形对角线BD,若图2中的∠EAF的边AE、AF分别交对角线BD于点G、点H.如图3,求
的值;
(4)剪一剪:将图3中的正方形纸片沿对角线BD剪开,如图4.求证:
.
折一折:将正方形纸片ABCD折叠,使边AB、AD都落在对角线AC上,展开得折痕AM、AN,连接MN,如图1.
![](https://img.xkw.com/dksih/QBM/2022/5/11/2977161474228224/2987925623463936/STEM/5d66f6f3-e38a-4ada-83b1-4842af752919.png?resizew=635)
(1)∠MAN=______
![](https://img.xkw.com/dksih/QBM/2022/5/11/2977161474228224/2987925623463936/STEM/2e6045f0b47b47b4a67a8fe62228fd26.png?resizew=11)
(2)转一转:将图1中的∠MAN绕点A旋转,使它的两边分别交边BC、CD于点E、F,连接EF,如图2.线段BE、EF、DF之间的数量关系为_________;
(3)连接正方形对角线BD,若图2中的∠EAF的边AE、AF分别交对角线BD于点G、点H.如图3,求
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9af4ea989fa0a89c7fef51255a92116b.png)
(4)剪一剪:将图3中的正方形纸片沿对角线BD剪开,如图4.求证:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/530706ea13c440b2a6ace1967043e3fb.png)
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【推荐1】如图,在四边形
中,
,
,
,
.
![](https://img.xkw.com/dksih/QBM/2019/11/5/2327356170027008/2327607906557952/STEM/481e0279ff8e4d848c410cb63e642a0d.png?resizew=392)
(1)如图(1),将
绕着
点旋转,它的两边分别交边
、
于
、
,试判断这一过程中线段
、
和
之间有怎样的数量关系?直接写出结论,不用证明;
(2)如图(2),将
绕着
点旋转,它的两边分别交边
、
的延长线于
、
,试判断这一过程中线段
、
和
之间有怎样的数量关系?并证明你的结论;
(3)如图(3),将
绕着
点旋转,它的两边分别交边
、
的反向延长线于
、
,试判断这一过程中线段
、
和
之间有怎样的数量关系?直接写出结论,不用证明.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2e735a28578ba191da6d4f3b0f8e8729.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5a16dc02090b6e9263555061f14fbc8c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3798a74058ec4bc40b6d9b5d268c359b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c9e77ba3587b3ea3c84549fd7ae6b0fe.png)
![](https://img.xkw.com/dksih/QBM/2019/11/5/2327356170027008/2327607906557952/STEM/481e0279ff8e4d848c410cb63e642a0d.png?resizew=392)
(1)如图(1),将
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/358c69b4f6c350c35d19d33c69f2a2a8.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5963abe8f421bd99a2aaa94831a951e9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0dc5c9827dfd0be5a9c85962d6ccbfb1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9d78abbad68bbbf12af10cd40ef4c353.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ac047e91852b91af639feec23a9598b2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/54a5d7d3b6b63fe5c24c3907b7a8eaa3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e69d2b798744645af88a4fa411344a83.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b3533837e3d08c461dea031a44e5424d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411461db15ee8086332c531e086c40c7.png)
(2)如图(2),将
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/358c69b4f6c350c35d19d33c69f2a2a8.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5963abe8f421bd99a2aaa94831a951e9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0dc5c9827dfd0be5a9c85962d6ccbfb1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9d78abbad68bbbf12af10cd40ef4c353.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ac047e91852b91af639feec23a9598b2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/54a5d7d3b6b63fe5c24c3907b7a8eaa3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e69d2b798744645af88a4fa411344a83.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b3533837e3d08c461dea031a44e5424d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411461db15ee8086332c531e086c40c7.png)
(3)如图(3),将
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/358c69b4f6c350c35d19d33c69f2a2a8.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5963abe8f421bd99a2aaa94831a951e9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0dc5c9827dfd0be5a9c85962d6ccbfb1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9d78abbad68bbbf12af10cd40ef4c353.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ac047e91852b91af639feec23a9598b2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/54a5d7d3b6b63fe5c24c3907b7a8eaa3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e69d2b798744645af88a4fa411344a83.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b3533837e3d08c461dea031a44e5424d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411461db15ee8086332c531e086c40c7.png)
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名校
解题方法
【推荐2】如图①,四边形ABCD与四边形AEFG是共一个顶点的两个大小不同的正方形.
(1)操作发现,如图②,正方形AEFG绕顶点A逆时针旋转,使点E落在边AD上时,填空:
①线段BE与DG的数量关系是 ;
②∠ABE与∠ADG的关系是 .
(2)猜想与证明:如图③正方形AEFG绕顶点A逆时针旋转某一角度α(0<α<90°)时,猜想(1)中的结论是否成立?并证明你的结论;
(3)拓展应用:如图④,正方形AEFG绕点A逆时针旋转,使点F落在边AD上时,若AB=
,AE=1,则BE= .
(1)操作发现,如图②,正方形AEFG绕顶点A逆时针旋转,使点E落在边AD上时,填空:
①线段BE与DG的数量关系是 ;
②∠ABE与∠ADG的关系是 .
(2)猜想与证明:如图③正方形AEFG绕顶点A逆时针旋转某一角度α(0<α<90°)时,猜想(1)中的结论是否成立?并证明你的结论;
(3)拓展应用:如图④,正方形AEFG绕点A逆时针旋转,使点F落在边AD上时,若AB=
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/95bacae35b6e16a0a33c2bdc6bc07df7.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2023/1/12/8ac7b6f3-94ca-43ae-975c-6f2b7f3e2633.png?resizew=585)
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【推荐3】问题探究
将几何图形按照某种法则或规则变换成另一种几何图形的过程叫做几何变换.旋转变换是几何变换的一种基本模型.经过旋转,往往能使图形的几何性质明白显现.题设和结论中的元素由分散变为集中,相互之间的关系清楚明了,从而将求解问题灵活转化.
问题提出:如图1,
是边长为1的等边三角形,
为
内部一点,连接
,求
的最小值.
方法分析:通过转化,把由三角形内一点发出的三条线段(星型线)转化为两定点之间的折线(化星为折),再利用“两点之间线段最短”求最小值(化折为直).
问题解决:如图2,将
绕点
逆时针旋转
至
,连接
、
,记
与
交于点
,易知
,
.由
,
,可知
为正三角形,有
.
故
.因此,当
共线时,
有最小值是
.
学以致用:(1)如图3,在
中,
,
,
为
内部一点,连接
、
,则
的最小值是__________.
(2)如图4,在
中,
,
,
为
内部一点,连接
、
,求
的最小值.
(3)如图5,
是边长为2的正方形
内一点,
为边
上一点,连接
、
,求
的最小值.
将几何图形按照某种法则或规则变换成另一种几何图形的过程叫做几何变换.旋转变换是几何变换的一种基本模型.经过旋转,往往能使图形的几何性质明白显现.题设和结论中的元素由分散变为集中,相互之间的关系清楚明了,从而将求解问题灵活转化.
问题提出:如图1,
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/15c0dbe3c080c4c4636c64803e5c1f76.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/dad2a36927223bd70f426ba06aea4b45.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/15c0dbe3c080c4c4636c64803e5c1f76.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/92c7267e5313b9b00ef22c94a479fc34.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c7ed53a398b1d6b7b4abbb43a9abcf1f.png)
![](https://img.xkw.com/dksih/QBM/2019/6/21/2230501665013760/2286799122219008/STEM/c39effe7779d4fbca9d4e6010c22f18e.png?resizew=303)
方法分析:通过转化,把由三角形内一点发出的三条线段(星型线)转化为两定点之间的折线(化星为折),再利用“两点之间线段最短”求最小值(化折为直).
问题解决:如图2,将
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e08b395fcd6ac97b243d81ffa189fac3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7f9e8449aad35c5d840a3395ea86df6d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/be6a6301878fed2a01413020b27310a5.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/cf5b70538a04aa8b90833ade21697d36.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2a99e1ad0d6fb0f13be56d09086366c5.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6eb97aff0960e2640314888a38e7169c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6eb97aff0960e2640314888a38e7169c.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/0eccf1bec4d47182b1f8558a40107781.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d03b5f4bc394b099df794f7ec67b9b27.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7ca593abee89ddd043d52dcb84234b3e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/49f5475706f467bf6f9ad676f10218d5.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c6ccbe874f84d01483637204b44d8245.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7962ca672dbe440498618642ba4cf5b0.png)
故
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6bcf8bf59af703f18e03490bbcfdd436.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b2d010504270e2626e6d7bd6ae1de6c6.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c7ed53a398b1d6b7b4abbb43a9abcf1f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/cef812f839622326a7d7027cc806aaeb.png)
学以致用:(1)如图3,在
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/15c0dbe3c080c4c4636c64803e5c1f76.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ab926d89b65f26c12e3da73ef1e5cf68.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/81c0bb354498eb9e755a63a2149e9706.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/dad2a36927223bd70f426ba06aea4b45.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/15c0dbe3c080c4c4636c64803e5c1f76.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/60d4a832771ba45d407f31000c8fcf37.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/48f3c9abbd78e9a6840ee5f30381daac.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c7ed53a398b1d6b7b4abbb43a9abcf1f.png)
![](https://img.xkw.com/dksih/QBM/2019/6/21/2230501665013760/2286799122219008/STEM/3a5c48f03a934528836cd35ecdaab1a1.png?resizew=531)
(2)如图4,在
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/15c0dbe3c080c4c4636c64803e5c1f76.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9b123b07a73add4f4c100d1babe8e41d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ecd0da5c46deed512fb06441447adf6b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/dad2a36927223bd70f426ba06aea4b45.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/15c0dbe3c080c4c4636c64803e5c1f76.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/60d4a832771ba45d407f31000c8fcf37.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/48f3c9abbd78e9a6840ee5f30381daac.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1fdb0272e5daf5c2ff401d9f369ba19b.png)
(3)如图5,
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/dad2a36927223bd70f426ba06aea4b45.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/acc290b44635265137fdf13146b6a6d9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0dc5c9827dfd0be5a9c85962d6ccbfb1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/fc6b04dcd5a34b8125696faf552ab63f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7a5f1641947153c80b987320885a2b57.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/df856ee8ba2ea9813ad1a8a4388c8428.png)
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