1 . 已知点O为凸四边形ABCD内的一点,AO=OB,CO=OD,
,E、F、G分别是线段AB、BC、CD的中点,求证:
为正三角形.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/cb879cccf44dbf4d72c9a85906dfb5a8.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b9756177ef0c7c685e0fc62077a1cd4e.png)
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2 . 已知
、
均为等腰三角形,
,
.如图,将
绕点
逆时针方向旋转一个角度
,
的延长线与直线
交于点
,如图.
![](https://img.xkw.com/dksih/QBM/2018/12/4/2089518449434624/2090822997901312/STEM/af61e656989344b9b2a75721b68bbc34.png?resizew=158)
![](https://img.xkw.com/dksih/QBM/2018/12/4/2089518449434624/2090822997901312/STEM/689f05d11d6a4871818b0b75837a55ae.png?resizew=180)
则
绕点
逆时针方向从
旋转到
的过程中,点
运动的路线长为_________ .
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0faed94a64b2dcfc6801b4fca0f16675.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f460edcced5597615113c0fdc95b1dfc.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8f89deb952f57f4b3fa4887b098b7b91.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/abc28e69c1ba0aac981256887f7dfa94.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f460edcced5597615113c0fdc95b1dfc.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5963abe8f421bd99a2aaa94831a951e9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e170f206fdbbd834aad7580c727e2cc6.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d40b319212a7e7528b053e1c7097e966.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4eedae8d316c76e3d0b451256de03fb9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/dad2a36927223bd70f426ba06aea4b45.png)
![](https://img.xkw.com/dksih/QBM/2018/12/4/2089518449434624/2090822997901312/STEM/af61e656989344b9b2a75721b68bbc34.png?resizew=158)
![](https://img.xkw.com/dksih/QBM/2018/12/4/2089518449434624/2090822997901312/STEM/689f05d11d6a4871818b0b75837a55ae.png?resizew=180)
则
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f460edcced5597615113c0fdc95b1dfc.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5963abe8f421bd99a2aaa94831a951e9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/235d495d88b8e51f89e2e4da27328025.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/bfe639eab78eafd2d40ea70aa5d3f21d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/dad2a36927223bd70f426ba06aea4b45.png)
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