如图,四边形ABCD为平行四边形纸片,把纸片ABCD折叠,使点B恰好落在CD边上的点E处,折痕为AF.已知
,
,
.
![](https://img.xkw.com/dksih/QBM/editorImg/2022/7/12/56862e99-349d-4de1-9299-35c5ee3deb6e.png?resizew=99)
(1)求证:平行四边形ABCD是矩形;
(2)求BF的长.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/fc34db5860990e51ba31edc8cdd077c2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/04ee826937d2add7a93aaa1422f8b736.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ea147ada4f0aefdd3808a6a1133792eb.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2022/7/12/56862e99-349d-4de1-9299-35c5ee3deb6e.png?resizew=99)
(1)求证:平行四边形ABCD是矩形;
(2)求BF的长.
更新时间:2022-07-09 08:05:50
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适中
(0.65)
【推荐1】如图①,在
中,
,
边上的高为4.求作菱形
,使点E在边
上,点F,G在边
上.
小宁的作法1.如图②,在边
上取一点E.
2.以点A为圆心,
长为半径画弧,交
于点G.
3.在
上截取
,连接
,则四边形
为所求作的菱形.
是菱形.
(2)小宁进一步探索,发现可作出的菱形的个数随着点E的位置变化而变化.请你继续探索,直接写出菱形的个数及对应的AE的长的取值范围.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5138a9f70d5e8b0580e30fef6eb7baef.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/325319794e6e9f704a832d2ca82a1a54.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0dc5c9827dfd0be5a9c85962d6ccbfb1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a8d0e8404f347a0eb4c76f4d25d9bdac.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/03902478df1a55bc99703210bccab910.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0dc5c9827dfd0be5a9c85962d6ccbfb1.png)
小宁的作法1.如图②,在边
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/03902478df1a55bc99703210bccab910.png)
2.以点A为圆心,
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/68a83fdd2ba72a2dba0b6b10bb3e06b9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0dc5c9827dfd0be5a9c85962d6ccbfb1.png)
3.在
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0dc5c9827dfd0be5a9c85962d6ccbfb1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ac719ca8c04231bb7b28bad575d8185d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/49b50357a6545cae8348e3059312f520.png)
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![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a8d0e8404f347a0eb4c76f4d25d9bdac.png)
(2)小宁进一步探索,发现可作出的菱形的个数随着点E的位置变化而变化.请你继续探索,直接写出菱形的个数及对应的AE的长的取值范围.
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【推荐2】如图,在正方形ABCD中,对角线AC,BD相交于点O,点E,F是对角线AC上的两点,且AE=CF.连接DE,DF,BE,BF.
![](https://img.xkw.com/dksih/QBM/2022/9/27/3075665320681472/3085944447377408/STEM/4a436cf21d694dd8bbf53a88fe88fd21.png?resizew=164)
(1)证明:△ADE≌△CBF.
(2)若AB=4
,AE=2,求四边形BEDF的周长.
![](https://img.xkw.com/dksih/QBM/2022/9/27/3075665320681472/3085944447377408/STEM/4a436cf21d694dd8bbf53a88fe88fd21.png?resizew=164)
(1)证明:△ADE≌△CBF.
(2)若AB=4
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7881094ce2f907c3aaf664318ecd3e2d.png)
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【推荐1】如图,在
中,
,直线
,垂足为点
.
![](https://img.xkw.com/dksih/QBM/editorImg/2024/1/17/07f064eb-9799-480a-973b-3ec90f492e8d.png?resizew=141)
(1)如果点
在直线
上,且点
到
两边的距离相等,试用直尺和圆规作出满足上述条件的点
(不写作法,仅保留作图痕迹,在图中清楚地标注出点
);
(2)在第(1)题的条件下,连接接
和
,如果
,请判断
的形状,并说明理由.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/15c0dbe3c080c4c4636c64803e5c1f76.png)
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(1)如果点
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2a30f3a8b673cc28bd90c50cf1a35281.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0f85fca60a11e1af2bf50138d0e3fe62.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2a30f3a8b673cc28bd90c50cf1a35281.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/2a30f3a8b673cc28bd90c50cf1a35281.png)
(2)在第(1)题的条件下,连接接
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/85c4bdfb0db1e31e8459df1d15f9ab55.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4eedae8d316c76e3d0b451256de03fb9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/144a6a0e1e16bc2105bbfac661e3bab9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/15c0dbe3c080c4c4636c64803e5c1f76.png)
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【推荐1】如图,在▱ABCD中,AE、CF分别平分∠BAD、∠BCD.求证:AE∥CF.
![](https://img.xkw.com/dksih/QBM/2021/8/6/2780114512953344/2781559911718912/STEM/c311fd05f06a4b0386afb3b074bb0ad2.png?resizew=175)
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【推荐2】在
ABCD中,对角线AC与BD交于点O,∠BAD的平分线交直线BC于点E,交直线DC于点F.
![](https://img.xkw.com/dksih/QBM/2013/6/13/1573662670585856/1573662676860928/STEM/5d40ecfe88c54111bd5c9a2c5d78700a.png)
(1)在图1中,证明CE=CF;
(2)若,∠BAD=90°, G是EF的中点(如图2),连结OG,判断OG与BD的位置关系与数量关系,并给出证明;
(3)若∠ABC=120°,FG∥CE,FG=CE,连结OG(如图3),判断OG与BD的位置关系与数量关系,并给出证明.
![](https://img.xkw.com/dksih/QBM/2013/6/13/1573662670585856/1573662676860928/STEM/d5b85071f47b4ef1b8cd52a69b68c5e8.png)
![](https://img.xkw.com/dksih/QBM/2013/6/13/1573662670585856/1573662676860928/STEM/5d40ecfe88c54111bd5c9a2c5d78700a.png)
(1)在图1中,证明CE=CF;
(2)若,∠BAD=90°, G是EF的中点(如图2),连结OG,判断OG与BD的位置关系与数量关系,并给出证明;
(3)若∠ABC=120°,FG∥CE,FG=CE,连结OG(如图3),判断OG与BD的位置关系与数量关系,并给出证明.
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【推荐1】如图,某同学想测量旗杆的高度,他在某一时刻测得1米长的竹竿竖直放置时影长为1.5米,在同一时刻测量旗杆的影长时,因旗杆靠近一楼房,影子不全落在地面上,有一部分落在墙上,他测得落在地面上的影长为21米,落在墙上的影高为6米,求旗杆的高度.
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【推荐2】如图,在
ABCD中,过点D作DE⊥AB于点E,点F在边CD上,CF=AE,连接AF,BF.
![](https://img.xkw.com/dksih/QBM/2022/9/10/3063610571227136/3069017605799936/STEM/45a1100d85ad42b8a1d615b9a546a131.png?resizew=153)
(1)求证:四边形BFDE是矩形;
(2)已知∠DAB=60°,AF是∠DAB的平分线,若AD=4,求
ABCD的面积.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/81a5328919a7cec382c2e91c9c528fc1.png)
![](https://img.xkw.com/dksih/QBM/2022/9/10/3063610571227136/3069017605799936/STEM/45a1100d85ad42b8a1d615b9a546a131.png?resizew=153)
(1)求证:四边形BFDE是矩形;
(2)已知∠DAB=60°,AF是∠DAB的平分线,若AD=4,求
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/81a5328919a7cec382c2e91c9c528fc1.png)
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