The lines will get shallower and eventually become horizontal and vertical respectively.

直线会变得更平缓,最后会分别变成水平和垂直两种情况

耶鲁公开课 - 博弈论课程节选

Excuse me. So what I'm going to do is, let's draw a picture that has S1 on the horizontal axis and S2 on the vertical axis.

好了,我们接下来来绘制图像,S1是横轴,S2是纵轴

耶鲁公开课 - 博弈论课程节选

Quite often, it's natural to pick x and y in a certain way, because starting a projectile near the Earth, it makes sense to pick the horizontal as x and vertical as y.

我们经常会很自然地选取 x 轴和 y 轴,因为如果在地表附近做抛物运动,我们通常以水平方向为 x 轴,竖直方向为 y 轴

耶鲁公开课 - 基础物理课程节选