Imagine that first wave describes the y-component of some rotating vector.

想象一下，第一波描述旋矢量的 y 分量。

Bobby, please break this vector  A, which is at an angle theta with the vertical, into its x and y-direction components.

Bobby，请将这与向成 θ 角的矢量 A 分解为 x 向和 y 向的分量。

So all of the upward force must be the y component or the upward component of this force vector on the first wire.

因此，所有向上的力必须是第一根线上该力矢量的 y 分量或向上分量。