This vector i prime has got a horizontal part, This kind of trigonometry you should know all the time.

矢量 i' 有一个水平方向的分量,这类三角关系你们应该已经很熟悉了

耶鲁公开课 - 基础物理课程节选

Now, when you work with components, Ax and Ay, if I didn't mention it, they are the components of the vector, you can do all your bookkeeping in terms of Ax and Ay.

当你们在计算分量 Ax 和 Ay 的时候,即使我没有说明,你们也要记得它们是矢量的分量,你们可以都用 Ax 和 Ay 的形式来表示

耶鲁公开课 - 基础物理课程节选