利用類似極限的概念：將O點從所在平麵提高delt，則三維成立。然後令delt趨於零。

來源: 皆兄弟也於 2010-09-19 21:54:35 [博客] [舊帖] [給我悄悄話] 本文已被閱讀：次

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