If you try to imagine a smile with no body at all, it can't be done. Why?

如果你要相信一个没有身体的微笑,那是根本做不到的 为什么呢

耶鲁公开课 - 死亡课程节选

But in your heart you know it can't be done by today.

但你心里清楚今天是不可能做完的。

I don't know 课堂 - SpeakingMax英语口语达人

Mathematically, it's done by taking the expression for R and differentiating everything in sight that can be differentiated as vector t.

从数学上看是这样的,写出 R 的表达式,并对所有可以进行矢量微分的部分,对时间 t 求微商

耶鲁公开课 - 基础物理课程节选

I don't know. I think it can be done, I know...

我不知道。是可能的吧，我觉得……

理想是当密码专家 - SpeakingMax英语口语达人