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

Then this is the component in your direction we call that the radial component which is v cosine theta.

这是y方向的，组成因素,我们称之为辐射组成,等于vcosθ

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

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