These two vectors are perpendicular exactly when their dot product is zero.
2
呃，我们学过怎么用点乘,来判断两个向量是否垂直。
Well, we've learned how to detect whether two vectors are perpendicular to each other using dot product.
3
还有个很有趣的现象要注意一下，就是我们可以用乘积法则,对向量表达式求导，无论是点乘或叉乘。
OK, now, so there's an interesting thing to note, which is that we can use the usual product rule for derivatives with vector expressions, with dot products or cross products.
点击反馈