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[几何] 简单(?)的几何

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xcx posted 2023-1-7 10:22 |Read mode
若多边形有 $2$ 条及以上对称轴,则它们交于一点

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重心定义.  posted 2023-1-7 13:10

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original poster xcx posted 2023-1-7 20:47
谢谢!

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hbghlyj posted 2023-1-8 05:11
若多边形有 2 条对称轴 $l_1,l_2$,则 $l_1$ 关于 $l_2$ 对称像 $l_3$ 也是对称轴,则 $l_2$ 关于 $l_3$ 对称像 $l_4$ 也是对称轴⋯

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uk702 posted 2023-1-8 07:04
Last edited by uk702 2023-1-8 07:11假设对称轴 $l_1$ 和 $l_2$ 相交于 O,$l_3$ 是另一条对称轴,是否可以通过证明 O 关于 $l_3$ 的对称点还是 O?进而证明所有的对称轴都相交于 O。

假设 O 关于 $l_3$ 的对称点是 $O_2$,而  $O_2$ 关于  $l_1$ 的对称点是  $O_3$,则 $OO_2$ = $OO_3$=$OO$ = 0 (?)
所以它们通通的重合。

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