So it is this component, v cosine theta - which we call the radial velocity-- that is minus 100 kilometers per second.

这个成分，是vcosθ,我们叫做径向速度-,等于-100，公里每秒。

youdao

I am going to decompose them, so I have one component here and this component equals mg times the cosine of alpha.

分解重力，这里得到一个分量,这个分量等于mgcosα

youdao

So this one equals m1 g cosine alpha - and this one, the x component-- which is in the minus x direction now-- equals m1 g sine alpha.

得到m1gcosα,而x方向上-,这里是x负方向-,大小是m1gsinα

youdao

Once you do that, I think it's fairly clear that it has got a y component that's given by cosine the x component is negative.

用了这个结论,我想很明显,y 分量由 cos φ 给出,它的 x 分量是负的

耶鲁公开课 - 基础物理课程节选