这上面有一个帽子表示它是单位矢量，T表示它是切线。

It has a hat because it's a unit vector, and t because it's tangent.

youdao

这上面有一个帽子表示它是单位矢量，T表示它是切线。

It has a hat because it's a unit vector, and t because it's tangent.

youdao