Use dot product to determine if two vectors point in the opposite direction [closed]
The dot product relates directly to the angle between two vectors.
More specifically, one can define the following:
$$cos(\theta):=\frac{v\cdot u}{\|v\|\|u\|}$$
Where $\theta$ is the angle between $v$ and $u$.
Thus, you can see that $\theta$ relates directly to $v\cdot u$, assuming we don't change the norms of $v$ or $u$. In the more specific case when $v,u$ are unit vectors, the relation becomes:
$$cos(\theta)=v\cdot u$$
Which shows this correlation even more clearly.