1 . 数学思想方法是解决问题的重要途径.在探究性学习中,我们可以采用从特殊到一般的数学思想,先从最简单的情形入手,从中找到解决问题的一般规律.如图,在
中,D为
边上一动点,在线段
右侧作线段
,使得
,且
.
![](https://img.xkw.com/dksih/QBM/2024/3/12/3451983019630592/3453269066014720/STEM/39cf284bb16146b792f529e2ed6ecc59.png?resizew=550)
【特殊情况】(1)若
,点E在
外,连接
交
于点F.
①如图1,
,
,猜想线段
与线段
有怎样的数量关系,说明理由;
②如图2,若
,猜想线段
与线段
有怎样的数量关系,说明理由;
【拓展运用】(2)如图3,若点E在
内,
与
交于点F,
,请用含k的式子表示
的值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/15c0dbe3c080c4c4636c64803e5c1f76.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0dc5c9827dfd0be5a9c85962d6ccbfb1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/03902478df1a55bc99703210bccab910.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/68a83fdd2ba72a2dba0b6b10bb3e06b9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/00c3d17c2b84511e18912c20634a1d11.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1bd1de2149bee37af329b7ad5b15de9d.png)
![](https://img.xkw.com/dksih/QBM/2024/3/12/3451983019630592/3453269066014720/STEM/39cf284bb16146b792f529e2ed6ecc59.png?resizew=550)
【特殊情况】(1)若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5095a28bb1b91bf6bed9e2cfbd76bb18.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/15c0dbe3c080c4c4636c64803e5c1f76.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/85c4bdfb0db1e31e8459df1d15f9ab55.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/60ef95894ceebaf236170e8832dcf7e3.png)
①如图1,
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b57fdd2a3642716fcf5100011eb3ec88.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8b5f215a42c4b7078d8d65923eb9980e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9d78abbad68bbbf12af10cd40ef4c353.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6aa2b5e09f8ec785c59900a529390a02.png)
②如图2,若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8a9e54d5a5e5924a87cce099dfe50c44.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9d78abbad68bbbf12af10cd40ef4c353.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6aa2b5e09f8ec785c59900a529390a02.png)
【拓展运用】(2)如图3,若点E在
![](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/85c4bdfb0db1e31e8459df1d15f9ab55.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/eceb0629d2166e32028a721138df9b51.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1b69eceac97ee6859e4fa51d54d40391.png)
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19-20九年级·江西南昌·阶段练习
2 . 定义:如果三角形上有两点,其中一点为一边的中点,且这两点的连线将三角形分成周长相等的两部分,我们就称这条线段为该三角形的“等分周线”.如图1,在
中,D是
的中点,点E在
上,若
,则
为
的一条“等分周线”.
概念理解
(1)任意三角形的“等分周线”有______条,若某三角形的一条“等分周线”有一个端点是三角形的顶点,则这个三角形是______.
规律探究
(2)如图1,在
中,
为
的一条“等分周线”.若
,
,
,求
的长.(用含m,
的代数式表示).
拓展应用
(3)如图2,在四边形
中,
,
平分
,
,点E在线段
上,连接
,
,且
,
,
,求
的长.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/15c0dbe3c080c4c4636c64803e5c1f76.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0dc5c9827dfd0be5a9c85962d6ccbfb1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f52a58fbaf4fea03567e88a9f0f6e37e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d0e28d6047ece23be329d3d38d9a3f4b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e6e490f703eb6c9bb1278c78ebc2d661.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/15c0dbe3c080c4c4636c64803e5c1f76.png)
概念理解
(1)任意三角形的“等分周线”有______条,若某三角形的一条“等分周线”有一个端点是三角形的顶点,则这个三角形是______.
规律探究
(2)如图1,在
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/15c0dbe3c080c4c4636c64803e5c1f76.png)
![](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/abcb980da8e86b4cfd322616dc84fc6e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1fd465973943bcd766b5275ee204bbf2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/15fcde639611cd140a6ffcd336bc5e27.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e6e490f703eb6c9bb1278c78ebc2d661.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e170f206fdbbd834aad7580c727e2cc6.png)
拓展应用
(3)如图2,在四边形
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/510634e49198fc429d942d00fa5446ab.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/60ef95894ceebaf236170e8832dcf7e3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/727ad3e630a224303d6d3b8ad5c114ba.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/81681f4f098511de0da54271f2b42a23.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/60ef95894ceebaf236170e8832dcf7e3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/21037e170bdbb322558e79c40c00b454.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ccaee8f228ff24e7c89879bb5b999cf2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/68b40d0d2f3cdd8981bb792ad87efb42.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6af352128fc4601065947c85c7d4a42a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/84ee8de2d272e8a3cad423ef206cd7eb.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/21037e170bdbb322558e79c40c00b454.png)
![](https://img.xkw.com/dksih/QBM/2020/11/3/2584867635585024/2585213465640960/STEM/6e9a33fa35ce4ecb995e6ed984e9098e.png?resizew=542)
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