It's not accelerating in the x direction, nor is it accelerating in the vertical direction or the y direction.

没有向x方向加速没有向竖直方向 就是y方向加速。

And then one in the y direction, this way, forward and backwards, right?

然后一个在 y 方向，这样，向前和向后，对吧？

And now for the Y direction we can use the definition of sine of theta.

现在对于 Y 方向，我们可以使用正弦函数的定义。

I had the unit vector in the Y direction, j Hat, and a new guy the unifector in the Z direction, called k Hat.

我有Y方向的单位向量 j帽 还有一个Z方向的单位向量 叫做k帽。

E.g. let's say that V was a vector with length two, pointing straight up in the Z direction, and W is a vector with length to pointing in the pure Y direction.

例如 我们设V是一个长度为2的向量 指向Z方向 W是一个长度为纯Y方向的向量。