T5 For instance, between t4 and t5, if I draw this line then this Angle here is negative 5 and so the average velocity between t4 and t5 is now negative.

比如取t 4和，我这样连线，那角度就是负的，因此，t4和t5之间的平均速度5，为负。

youdao

T5 For instance, between t4 and t5, if I draw this line then this Angle here is negative 5 and so the average velocity between t4 and t5 is now negative.

比如取t 4和，我这样连线，那角度就是负的，因此，t4和t5之间的平均速度5，为负。

youdao