[回顾课本]苏教版八年级下册数学教材“9.5三角形的中位线"一课中给出了“三角形的中位线定理”的证明思路,请根据分析完成证明过程.
已知:如图1,
是
的中位线,求证:
,
.
分析:因为E是
的中点,可以考虑以点E为中心,把
按顺时针方向旋转
,得到
,这样就需要证明四边形
是平行四边形……
[探究发现]
如图2,等边
的边长为2,点D,E分别为
,
边中点,点F为
边上任意一点(不与B,C重合),沿
,
剪开分成①,②,③三块后,将②,③分别绕点D,E旋转
恰好能与①拼成平行四边形
,求平行四边形
周长的最小值.
[拓展作图]
如图3,已知四边形
,现要将其剪成四块,使得剪成的四块能通过适当的摆放拼成一个平行四边形,请在图3中画出剪痕,并对剪痕作适当的说明.
已知:如图1,
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e6e490f703eb6c9bb1278c78ebc2d661.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/15c0dbe3c080c4c4636c64803e5c1f76.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1d021981c03e75b1a246d899dcc64656.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/950e82a0f9712457f2dd9f8a93f8a217.png)
分析:因为E是
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/60ef95894ceebaf236170e8832dcf7e3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a25c28359f8d8da9eaf4672a6cf8ae4f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/95e1dcdc9d50fe147e3924ce30bba519.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/25c333f2e1769473c6ada9790f841572.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/211c130e20ea36d96e88927f88df956e.png)
[探究发现]
如图2,等边
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/15c0dbe3c080c4c4636c64803e5c1f76.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f52a58fbaf4fea03567e88a9f0f6e37e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/60ef95894ceebaf236170e8832dcf7e3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0dc5c9827dfd0be5a9c85962d6ccbfb1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e6e490f703eb6c9bb1278c78ebc2d661.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d004d2d115b477ade6af7ddb93db0df8.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/bfe639eab78eafd2d40ea70aa5d3f21d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0f0c8e7bd13719b25ca955ef4c633bd0.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0f0c8e7bd13719b25ca955ef4c633bd0.png)
[拓展作图]
如图3,已知四边形
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
更新时间:2024-05-17 10:11:35
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【推荐2】矩形
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(1)若
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的度数与
的长度;
(2)如图2将
向右平移得
,两直角边与拒形相交于点E、F;当平移的距离是多少时,能使
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相似,(先填空,再完成解答)解:设平移的距离为x,则
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