减去一个常数向量的大小（缩短向量），而不使用平方根?。

Subtract a constant from a vector's magnitude (shorten the vector) without using square root?

youdao

例如，在某些情况下，如果已知向量场与曲线相切，或者内积是一个常数等等，那么结果将会很简单。

And, in some cases, for example, if you know that the vector field is tangent to the curve or if a dot product is constant or things like that then that might actually give you a very easy answer.

youdao

一个法向量与任意常数相乘，还是法向量。

You can just multiply a normal vector by any constant, you will still get the normal vector.

youdao