下面是某同学设计的“作已知圆的内接正三角形”的尺规作图过程.
已知:
.
求作:
的内接正三角形.
作法:如图,
![](https://img.xkw.com/dksih/QBM/editorImg/2023/1/1/9e6d2b72-50d5-43a3-a370-e5607e461bce.png?resizew=131)
①作直径
;
②以
为圆心,
为半径作弧,与
交于C、D两点(点
在直线
上方);
③连接
,
,
.
所以
就是所求的三角形.
根据该同学设计的尺规作图过程,
(1)使用直尺和圆规,补全图形;(保留作图痕迹)
(2)完成下面的证明:
证明:在
中,连接
,
,
,![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d40b319212a7e7528b053e1c7097e966.png)
____________,
为等边三角形.
.
.
同理
,
______________.
(___________________________)(填推理的依据).
是等边三角形.
已知:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3d97cdc586744d208b6f69c9813af977.png)
求作:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3d97cdc586744d208b6f69c9813af977.png)
作法:如图,
![](https://img.xkw.com/dksih/QBM/editorImg/2023/1/1/9e6d2b72-50d5-43a3-a370-e5607e461bce.png?resizew=131)
①作直径
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f52a58fbaf4fea03567e88a9f0f6e37e.png)
②以
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7f9e8449aad35c5d840a3395ea86df6d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b90e0f35eda1a729fed485f83da5ea9d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3d97cdc586744d208b6f69c9813af977.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c5db41a1f31d6baee7c69990811edb9f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f52a58fbaf4fea03567e88a9f0f6e37e.png)
③连接
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/60ef95894ceebaf236170e8832dcf7e3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/03902478df1a55bc99703210bccab910.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9d78abbad68bbbf12af10cd40ef4c353.png)
所以
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7ac451db3443cabb204f96c31fd4a02e.png)
根据该同学设计的尺规作图过程,
(1)使用直尺和圆规,补全图形;(保留作图痕迹)
(2)完成下面的证明:
证明:在
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3d97cdc586744d208b6f69c9813af977.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/828628c0876b45381c9a0edeb0fec236.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/683c590673eece14fea3319c4fd5eb55.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0dc5c9827dfd0be5a9c85962d6ccbfb1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d40b319212a7e7528b053e1c7097e966.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9d2789a67af66e3c8bc2461d55d33b85.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2def235f8255135d44ceb0bf541abe73.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3043b429b75ef7d1955ae3ff59df1ade.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/102bffc82ddfe61c0576dc9fd052d007.png)
同理
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/551137582e6b5534016fe384b492b13e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b3a8aab27214bfdda67612b85ce5aae3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4e7ee38c87153922b8985afe599f8f3c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ad537fd45c4ae6a64aa784980cbd9da4.png)
22-23九年级上·北京西城·阶段练习 查看更多[2]
更新时间:2022-12-12 21:32:42
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【推荐2】用两种方法证明命题“在圆的内接四边形中,如果一组对边相等,那么另一组对边平行”.
已知:如图,四边形
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![](https://img.xkw.com/dksih/QBM/editorImg/2022/12/9/7e9feff0-9e9d-4c80-8e8e-88f078fc218b.png?resizew=134)
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___________________.即
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___________________.(依据是___________________)
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请把证1补充完整,并用不同的方法完成证法2.
已知:如图,四边形
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3d97cdc586744d208b6f69c9813af977.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c220eadc312101e2fb89dfe920f7b30d.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2022/12/9/7e9feff0-9e9d-4c80-8e8e-88f078fc218b.png?resizew=134)
求证:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4adf90a8c2b29334cdc5aa5b554991f9.png)
证法1:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1e9dd6147fd83173b71cc7467e481b3f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f50c0420bd55d2dd697f533e7c00ac5b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2de0d10ef8b748d4531250c37c5d3f9e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/bfdd75d590a43c7469b0b333fd9f213f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/736c5a11deac3f6b8fb87fbbed3478cc.png)
∵四边形
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3d97cdc586744d208b6f69c9813af977.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2de0d10ef8b748d4531250c37c5d3f9e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a874aae96dd89b960c7c35eb12ee8c24.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2e8644afba5451902a1d517ec584877a.png)
请把证1补充完整,并用不同的方法完成证法2.
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