1·So, if you wanted to know how long; an arch of cycloid is, you have this nice-looking curve; how long is it?
如果你想知道一个摆线有多长，这是一条很漂亮的曲线，这有多长？
2·So, let me explain what's the definition of a cycloid.
让我来说明一下摆线的定义。
3·Let's take, so, it's a famous curve called a cycloid.
来看看一条著名的曲线——摆线。
4·Maybe on the cycloid, we'd say it's a distance starting on the origin.
在摆线上，称之为到起点的距离。
5·Ok, so — so the cycloid, well, I guess it doesn't quite look like what I've drawn.
这是摆线，它跟我画的不大一样。