学习完平行线的性质与判定之后,我们发现借助构造平行线的方法可以帮我们解决许多问题.
![](https://img.xkw.com/dksih/QBM/editorImg/2022/8/7/07b756d9-1f39-4fbb-9081-a7b56b602521.png?resizew=612)
(1)萌萌遇到了下面的问题:如图1,l1
l2,点M在l1、l2内部,探究∠A,∠AMB,∠B的关系,萌萌过点M作MN
l1,可证∠AMB,∠A,∠B之间的数量关系是:∠AMB= .
(2)如图2,若l1
l2,点M在l1、l2外部,∠A,∠B,∠AMB的数量关系是怎么样的?
请你补全下面的证明过程.
过点M作ME
l2.
∴∠B= ,
∵l1
l2.
∴
.
∴∠A= .
∵∠AMB=∠AME﹣∠BME,
∴ .
(3)随着以后的学习你还会发现平行线的许多用途.试构造平行线解决以下问题:已知:如图3,三角形ABC,求证:∠A+∠B+∠C=180°.
![](https://img.xkw.com/dksih/QBM/editorImg/2022/8/7/07b756d9-1f39-4fbb-9081-a7b56b602521.png?resizew=612)
(1)萌萌遇到了下面的问题:如图1,l1
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2a9bfa68259d7a331be323b2038d628a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2a9bfa68259d7a331be323b2038d628a.png)
(2)如图2,若l1
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2a9bfa68259d7a331be323b2038d628a.png)
请你补全下面的证明过程.
过点M作ME
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2a9bfa68259d7a331be323b2038d628a.png)
∴∠B= ,
∵l1
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2a9bfa68259d7a331be323b2038d628a.png)
∴
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2a9bfa68259d7a331be323b2038d628a.png)
∴∠A= .
∵∠AMB=∠AME﹣∠BME,
∴ .
(3)随着以后的学习你还会发现平行线的许多用途.试构造平行线解决以下问题:已知:如图3,三角形ABC,求证:∠A+∠B+∠C=180°.
更新时间:2022-08-05 18:51:07
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解答题-证明题
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【推荐1】已知,如图,在四边形
中,
,点E,F为对角线
上两点,且
,
.求证:四边形
为平行四边形.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4adf90a8c2b29334cdc5aa5b554991f9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/60ef95894ceebaf236170e8832dcf7e3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f7c581dab991aeadf06d972e47673ea8.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/37277bc0191d90453005ef69562f552b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
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【推荐2】如图,港口B在港口A的北偏东
方向,且A、B之间的距离为
.港口C在港口B的北偏西
方向,且港口A的正北方向.求港口B与C之间的距离
.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/97f38acaaa4d4110b7ca927fdf7a8b6c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/336ee194e7117eff8c721f0ef1ac7be1.png)
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![](https://img.xkw.com/dksih/QBM/editorImg/2023/3/17/74edda4f-27f3-4da3-974a-20f0487a322f.png?resizew=68)
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名校
【推荐1】新知探究:
光在反射时,光束的路径可用图(1)来表示,
叫做入射光线,
叫做反射光线,从入射点
引出的一条垂直于镜面
的射线
叫做法线.
与
的夹角
叫入射角,
与
的夹角
叫反射角.根据科学实验可得:
.
.
问题解决:
生活中我们可以运用“激光”和两块相交的平面镜进行测距.如图(2)当一束“激光”
射入到平面镜
上、被
反射到平面镜
上,又被平面镜
反射后得到反射光线
.
(2)当
,
时,求
的度数.
(3)当
时,任何射到平面镜
上的光线
经过平面镜
和
的两次反射后,入射光线
与反射光线
总是平行的.请你根据所学过的知识及新知说明.
光在反射时,光束的路径可用图(1)来表示,
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e2c3d2cba96f6f03520c0b3f6e4da03e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b90e0f35eda1a729fed485f83da5ea9d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1dde8112e8eb968fd042418dd632759e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/49b50357a6545cae8348e3059312f520.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/aaf3369e0ea90e8d5cf4b6b3c45c0fd8.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e2c3d2cba96f6f03520c0b3f6e4da03e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/aaf3369e0ea90e8d5cf4b6b3c45c0fd8.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e170f206fdbbd834aad7580c727e2cc6.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b90e0f35eda1a729fed485f83da5ea9d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/aaf3369e0ea90e8d5cf4b6b3c45c0fd8.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5b5858ee1ce52b251816757257a11c29.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1aab5b0c0b46a4c1090cc5976509357a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0e53497af8899cb299d762f1a4f46a55.png)
问题解决:
生活中我们可以运用“激光”和两块相交的平面镜进行测距.如图(2)当一束“激光”
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f52a58fbaf4fea03567e88a9f0f6e37e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f90c780dac29ff8b7df5881d3b33abab.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f90c780dac29ff8b7df5881d3b33abab.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6cad4595d5352b2884568a59d8d766a4.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6cad4595d5352b2884568a59d8d766a4.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9d78abbad68bbbf12af10cd40ef4c353.png)
(2)当
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b0fff774b4b0087a6f304ce930d359be.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ceb8ac3f3b2598a84e0bf85b713ecdb2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d39b8d91afc34e4a9b0fdbb6bafb9087.png)
(3)当
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c0f11cd98a1aa440491c95af505b2a9e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f90c780dac29ff8b7df5881d3b33abab.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f52a58fbaf4fea03567e88a9f0f6e37e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f90c780dac29ff8b7df5881d3b33abab.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6cad4595d5352b2884568a59d8d766a4.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f52a58fbaf4fea03567e88a9f0f6e37e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9d78abbad68bbbf12af10cd40ef4c353.png)
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解答题-作图题
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【推荐2】如图,在
中,
,
的垂直平分线交
于点D,交
于点E,
的平分线交
于点F,两线交点为点P.
![](https://img.xkw.com/dksih/QBM/editorImg/2023/2/23/3b333bc3-b950-4306-b83b-6a346ffdb614.png?resizew=180)
(1)依题意补全图形(要求:尺规作图,保留作图痕迹,不写作法);
(2)连接
,若
,
的周长是
,
_____________;
(3)连接
,设
,则
__________;(用含
的式子表示).
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/15c0dbe3c080c4c4636c64803e5c1f76.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/998329f9cdb86f5d60d7d5d70fc3781e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f52a58fbaf4fea03567e88a9f0f6e37e.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/7cbce11aa19b8bd2bf6ee5a834e005de.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0dc5c9827dfd0be5a9c85962d6ccbfb1.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2023/2/23/3b333bc3-b950-4306-b83b-6a346ffdb614.png?resizew=180)
(1)依题意补全图形(要求:尺规作图,保留作图痕迹,不写作法);
(2)连接
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/85c4bdfb0db1e31e8459df1d15f9ab55.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a2fae188b381c5ba01b3d9d742c687dd.png)
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(3)连接
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2cdba1337ec85fa9722cb4b320a82ae6.png)
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![](https://staticzujuan.xkw.com/quesimg/Upload/formula/39764293c76b41c259e3c640f7420456.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e170f206fdbbd834aad7580c727e2cc6.png)
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