Trajectories, thank goodness, are almost never three-dimensional.

轨迹，感谢上帝，基本上永远不是三维的。

The process of speed is abstracted increasing the endless trajectories.

速率的历程被抽象成渐增的、永无尽头的轨迹。

The process of speed is subjectiveed increasing the endless trajectories.

速度的进程被笼统成渐增的、永无尽头的轨迹。

To answer this question, we need to plot trajectories of principal stresses.

研究了一种简便快速的主应力迹线自动化绘制方法。

Now comes my last part, and that is, how does air drag influence trajectories?

现在是最后一部分，就是，空气阻力如何影响轨道？