因为一直到现在我们都是在看图像，而且知道它们，是相切的，但是为什么在一般情况下它们都相切？

Because so far I have shown you pictures and have said see they are tangent.But why is it that they have to be tangent in general?

youdao

我们知道梯度向量垂直于这个向量，而速度向量是相切于等值面的，其他相切于等值面的向量，又如何呢？

We know that the gradient is perpendicular to this vector that's tangent to the level surface What about other vectors tangent to the level surface?

youdao

水是建造时间入口的屏障元素，该入口被用作在相切涡汇处的各个相切宇宙之间的门关。

Water is the barrier element for the construction of Time Portals used as gateways between Universes at the Tangent Vortex.

youdao

That limit will be some arrow we can call the velocity at the time and it will always be tangent to the curve.

那个极限也就是一个矢量,我们称之为瞬时速度,并且它总是和轨迹相切的

耶鲁公开课 - 基础物理课程节选

So the velocity at any part of the curve is tangent to the curve at that point.

曲线上任意一点的速度,都在该点和曲线相切

耶鲁公开课 - 基础物理课程节选

That means that you want to pick, ultimately, a point on this-- this line is tangent to the efficient portfolio frontier with all the other assets in it.

那意味着你会最终会在这上面选一个点-,这条直线是与有效边界相切的,后者包含了所有的资产组合。

耶鲁公开课 - 金融市场课程节选