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maybiddiena
2 năm trước
Cho đa giác đều`A_1A_2A_3...A_n` tâm `O`. Chứng minh `\vec{OA_1}+\vec{OA_2}+...+\vec{OA_n}=\vec0` (Chia hai trường hợp đa giác có số cạnh chẵn và số cạnh lẻ)
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