已知:如图,点D在等边三角形
的边
上,延长
至点E使
,连接
交A
与点F.
(1)求证:
;
(2)过点D作
于G,若等边三角形
的边长为6,求
的长.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7bef5239ddbb0972700ce01daf9ee7cf.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f52a58fbaf4fea03567e88a9f0f6e37e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0dc5c9827dfd0be5a9c85962d6ccbfb1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/41a3a922f7ea64083c415c72259179a3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e6e490f703eb6c9bb1278c78ebc2d661.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c5db41a1f31d6baee7c69990811edb9f.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2023/5/31/47da3535-5c56-4f41-8492-eddd2be1a35c.png?resizew=208)
(1)求证:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2d77b021bfecc78d8a55ed65ed69cd4f.png)
(2)过点D作
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d222d3bcc808dd5b62b2a9ccb543a6d7.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7bef5239ddbb0972700ce01daf9ee7cf.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c63e36329f5e0979f5ee776ac5d06327.png)
21-22七年级下·全国·单元测试 查看更多[3]
第17章 三角形 单元测试卷人教版(五四制)七年级数学下册(已下线)第13讲 等边三角形及含30°角的直角三角形的性质-【暑假自学课】2023年新八年级数学暑假精品课(人教版)(已下线)第11讲 等边三角形的性质与判定定理-【暑假自学课】2023年新八年级数学暑假精品课(浙教版)
更新时间:2023-05-16 15:32:06
|
相似题推荐
解答题-证明题
|
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(0.85)
【推荐1】我们知道,如果三角形一个外角的平分线平行于三角形的一边,那么这个三角形是等腰三角形.证明这种文字性命题一般思路为:画草图,写出已知求证并证明.
按以上思路完成下面的作图与填空.
求证:如果三角形一个外角的平分线平行于三角形的一边,那么这个三角形是等腰三角形.
已知:如图,
是
的外角,
平分
,
.
求证:
.
证明:用直尺和圆规作
的平分线
.(只保留作图痕迹)
∵
,
∴ ① , ② ,
∵
平分
,
∴ ③ ,
∴ ④ ,
∴
(等角对等边).
按以上思路完成下面的作图与填空.
求证:如果三角形一个外角的平分线平行于三角形的一边,那么这个三角形是等腰三角形.
已知:如图,
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/35803969509655f72b4118503ae1c966.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/15c0dbe3c080c4c4636c64803e5c1f76.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/03902478df1a55bc99703210bccab910.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/35803969509655f72b4118503ae1c966.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6dceb5cc71fc50f20649f6b9535fd914.png)
求证:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/047dc9795efa99b6fb9fdf9778085dab.png)
证明:用直尺和圆规作
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/35803969509655f72b4118503ae1c966.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/03902478df1a55bc99703210bccab910.png)
∵
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6dceb5cc71fc50f20649f6b9535fd914.png)
∴ ① , ② ,
∵
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/03902478df1a55bc99703210bccab910.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/35803969509655f72b4118503ae1c966.png)
∴ ③ ,
∴ ④ ,
∴
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/047dc9795efa99b6fb9fdf9778085dab.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2023/3/5/82c0a8bf-fa61-4d92-b85e-ba971495b954.png?resizew=72)
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【推荐2】如图,是一个“猪手”图,
,点E在两平行线之间,连接
,
,我们发现:![](https://staticzujuan.xkw.com/quesimg/Upload/formula/53e8c20ab2cfef48f31dda36ca92afab.png)
点作
.
(两直线平行,内错角相等.)
又![](https://staticzujuan.xkw.com/quesimg/Upload/formula/16f3d198e76391779fa3badc848c8ac8.png)
(已知)
(如果两条直线都与第三条直线平行,那么这两条直线也互相平行.)
(两直线平行,内错角相等.)
(等式的性质1.)
即:
.
如图是一个“子弹头”图,
,点E在两平行线之间,连接
,
.试探究
.写出证明过程.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b0fff774b4b0087a6f304ce930d359be.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d0213c5787a5a6b38d11bceca5567f67.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1a6c6e7c025362c46a64a8956761f08e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/53e8c20ab2cfef48f31dda36ca92afab.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2a30f3a8b673cc28bd90c50cf1a35281.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b25eff69a4a0dc7a7ab183843303d333.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2de0d10ef8b748d4531250c37c5d3f9e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/acf8d165efac7c0f09e5fb9269b8e870.png)
又
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/16f3d198e76391779fa3badc848c8ac8.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b0fff774b4b0087a6f304ce930d359be.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2de0d10ef8b748d4531250c37c5d3f9e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9390a8688fd466fb6b883b0d60dcd872.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2de0d10ef8b748d4531250c37c5d3f9e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b3bf9f944581cd2fdabb46800d60154e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2de0d10ef8b748d4531250c37c5d3f9e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3a07797ca007d0bbb1e4d254a336e2cb.png)
即:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8d72c9eb1d417df6a2f0b291c1f58e52.png)
如图是一个“子弹头”图,
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b0fff774b4b0087a6f304ce930d359be.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d0213c5787a5a6b38d11bceca5567f67.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1a6c6e7c025362c46a64a8956761f08e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a74581233288dc94f490d36ec58c3a12.png)
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解答题-证明题
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【推荐1】如图,
,
相交于点O,且
,
.
![](https://img.xkw.com/dksih/QBM/editorImg/2022/11/25/cccd639e-c841-4d02-84c9-89f9cc004de5.png?resizew=166)
(1)求证:
;
(2)若在直线
上截取
,求证:
.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/03902478df1a55bc99703210bccab910.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0dc5c9827dfd0be5a9c85962d6ccbfb1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b0fff774b4b0087a6f304ce930d359be.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1c35c43d90814396ff06336fa45e9650.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2022/11/25/cccd639e-c841-4d02-84c9-89f9cc004de5.png?resizew=166)
(1)求证:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/49c8dbc31b2e14067ef2f34b4e25f114.png)
(2)若在直线
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/03902478df1a55bc99703210bccab910.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6ff56ea00ca90825f3d95809de24f639.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/cce38d8a8a7043586aad206f8153d0bc.png)
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【推荐2】如图,在
中,点
为边
的中点,点
为边
上一点.过
作
于点
,且
平分
,过
作
交于点
.
求证:四边形
为平行四边形.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/15c0dbe3c080c4c4636c64803e5c1f76.png)
![](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/a0ed1ec316bc54c37c4286c208f55667.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/60ef95894ceebaf236170e8832dcf7e3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5963abe8f421bd99a2aaa94831a951e9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a4e22ba3e6e1c1d6b12d9b8baa8d1f02.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2a30f3a8b673cc28bd90c50cf1a35281.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/68a83fdd2ba72a2dba0b6b10bb3e06b9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7cbce11aa19b8bd2bf6ee5a834e005de.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2a30f3a8b673cc28bd90c50cf1a35281.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7c05420ab262912cf41f46bc3b0af070.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/895dc3dc3a6606ff487a4c4863e18509.png)
求证:四边形
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/91f0150c951d24e7e56277ab1f67c496.png)
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解答题-问答题
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【推荐1】如图,在菱形
中,
,E、F分别是
、
的中点,若
,求菱形的周长.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c5b8b98b2f83279a49e94d9f48c5e6f2.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/aeedb5f361a1baff6338436fff6c471d.png)
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【推荐2】如图,在等边三角形ABC中,点D,E分别在边BC,AC上,DE//AB,过点E作EF⊥DE,交BC的延长线于点F.
(1)求∠F的度数.
(2)若CE=1,求EF的长.
(1)求∠F的度数.
(2)若CE=1,求EF的长.
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