Rotational motion problem

Let’s denote the tangential and the normal accelerations by $a_t$ and $a_n$, respectively. Then, what angle does $$tan alpha = frac{|a_t|}{a_n}$$
stand for?

If it was just $cfrac{a_t}{a_n}$, I would think of it as the cute angle of a right triangle whose legs are formed by $a_t$ and $a_n$.

Any help is appreciated.