当点乘的数量积为零时,这两个向量垂直。

These two vectors are perpendicular exactly when their dot product is zero.

youdao

也不要帮对方说话（如当点餐时），除非他们邀请你帮他们点餐。

And don't speak for that other person (i.e order for them at dinner) unless they invite you to help with their order.

youdao

特别地，我们来看当点静止的时候,即在时间t=0的时刻，会发生什么。

So, in particular, let's look at what happens at time t equals zero when the point is not moving.

youdao

I cannot draw it that well, but imagine bringing the second point closer and closer to the first one.

我不能很好地把它画出来,但是你们可以想象,当第二个点,越来越靠近第一个点时

耶鲁公开课 - 基础物理课程节选

Right, because when we think of an energy diagram, that lowest spot there is going to have the lowest value of the binding energy or the most negative value of binding.

对因为当我们考虑,一个能量图时那里最低的点,是具有最低的结合能,或者最不活跃的结合能。

麻省理工公开课 - 化学原理课程节选

And the problem is, that we want to build this abstract data type, but we'd like to basically know what kind of object is it, and what functions actually belong to it, how do we use them?

然后我对它们运行了这个方法，就是这一小段代码这个方法,这有意义么？,当然没有了，对不对？,因为你知道，当你把两个极坐标，表示的点进行相加运算的时候？

麻省理工公开课 - 计算机科学及编程导论课程节选