题型:解答题-证明题
难度:0.65
引用次数:721
题号:6057669
用两种方法证明“三角形的外角和等于360°”.
已知:如图,∠BAE,∠CBF,∠ACD是△ABC的三个外角.
求证:∠BAE+∠CBF+∠ACD=360°.
证法1:∵________________________________________________________________,
∴∠BAE+∠1+∠CBF+∠2+∠ACD+∠3=180°×3=540°,
∴∠BAE+∠CBF+∠ACD=540°-(∠1+∠2+∠3).
∵______________,
∴∠BAE+∠CBF+∠ACD=540°-180°=360°.
请把证法1补充完整,并用不同的方法完成证法2.
已知:如图,∠BAE,∠CBF,∠ACD是△ABC的三个外角.
求证:∠BAE+∠CBF+∠ACD=360°.
证法1:∵________________________________________________________________,
∴∠BAE+∠1+∠CBF+∠2+∠ACD+∠3=180°×3=540°,
∴∠BAE+∠CBF+∠ACD=540°-(∠1+∠2+∠3).
∵______________,
∴∠BAE+∠CBF+∠ACD=540°-180°=360°.
请把证法1补充完整,并用不同的方法完成证法2.
![](https://img.xkw.com/dksih/QBM/editorImg/2023/12/8/1c5a7917-9615-4cbe-ba5c-b317ee8f6812.jpg?resizew=129)
更新时间:2018-02-15 10:31:50
|
相似题推荐
解答题-问答题
|
适中
(0.65)
【推荐1】如图,AD⊥BD,AE平分∠BAC, 若∠B=30°,∠ACB=100°,求∠DAE的度数.
![](https://img.xkw.com/dksih/QBM/2014/12/17/1573771678105600/1573771683962880/STEM/527d1f2e476f474fb7e2a9b75c698f12.png)
您最近一年使用:0次
解答题-问答题
|
适中
(0.65)
【推荐2】如图所示,在平面直角坐标系中,
交y轴于点C,连接
.
![](https://img.xkw.com/dksih/QBM/editorImg/2023/2/26/3d2de713-eae1-4f4a-bc1d-cdbf12c2723a.png?resizew=443)
(1)如图①所示,已知
,
,求
的面积;
(2)如图②所示,在(1)的条件上,点D在x轴上,
,求
的值;
(3)如图③所示,
轴于点M,N在y轴上,
,点P在x轴上,
,求
的度数.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f52a58fbaf4fea03567e88a9f0f6e37e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b90e0f35eda1a729fed485f83da5ea9d.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2023/2/26/3d2de713-eae1-4f4a-bc1d-cdbf12c2723a.png?resizew=443)
(1)如图①所示,已知
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/913f78382630e50543e5f7192cae3ed3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5590337b3868db8523eeb7f448efcf05.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/866b81a8384cce4f24867baca2e6820c.png)
(2)如图②所示,在(1)的条件上,点D在x轴上,
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/49e0705883d889cc68728df47c2ed5c8.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d09e97805187652372cfec504018af18.png)
(3)如图③所示,
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/91a9ef65be4d2c76c63034474267ee6c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6b7d16f777a349d3bdde250aa3358eb0.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/16f19c1796888bc572ab6efd1eefaa8d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e2407694babd974243443463210d09aa.png)
您最近一年使用:0次
解答题-证明题
|
适中
(0.65)
【推荐2】如图1,在△ABC中,BE平分∠ABC,CF平分∠ACB,BE与CF交于点D.
![](https://img.xkw.com/dksih/QBM/editorImg/2022/8/8/a632a80f-704b-479b-8c83-0be9cecb97bf.png?resizew=654)
(1)若∠BAC=74°,则∠BDC= ;
(2)如图2,∠BAC=90°,作MD⊥BE交AB于点M,求证:DM=DE;
(3)如图3,∠BAC=60°,∠ABC=80°,若点G为CD的中点,点M在直线BC上,连接MG,将线段GM绕点G逆时针旋转90°得GN,NG=MG,连接DN,当DN最短时,直接写出∠MGC的度数.
![](https://img.xkw.com/dksih/QBM/editorImg/2022/8/8/a632a80f-704b-479b-8c83-0be9cecb97bf.png?resizew=654)
(1)若∠BAC=74°,则∠BDC= ;
(2)如图2,∠BAC=90°,作MD⊥BE交AB于点M,求证:DM=DE;
(3)如图3,∠BAC=60°,∠ABC=80°,若点G为CD的中点,点M在直线BC上,连接MG,将线段GM绕点G逆时针旋转90°得GN,NG=MG,连接DN,当DN最短时,直接写出∠MGC的度数.
您最近一年使用:0次