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Questions in category: 曲线曲面论 (Curve and surface theory).

证明: 曲线 $r(t)$ 是平面曲线当且仅当 $(\dot{r}(t),\ddot{r}(t),\ddot{r}(t))=0$.

Posted by haifeng on 2012-06-30 10:50:20 last update 2012-07-26 09:21:37 | Answers (1) | 收藏

这里 $(\vec{a},\vec{b},\vec{c})$ 指混合积, 即等于 $\bigl\langle\vec{a}\times\vec{b},\vec{c}\bigr\rangle$. 对于三维(列)向量, 也等于行列式 $\det(\vec{a},\vec{b},\vec{c})$.