在构图中，一种极普通而优美的线叫做S曲线。

One of the most common and graceful lines used in composition is called the s curve.

youdao

完美常常来自于模型或是装配线，大自然或手工制造的物品往往是不完美的。

Perfection comes out of molds or off assembly lines. Things made by nature or by hand are imperfect.

youdao

这就是为什么，这个线积分，有着完美的定义，但却不能对它使用格林公式的原因。

And so that's why you have this line integral that makes perfect sense, but you can't apply Green's theorem to it.

youdao