As part of [this problem](https://math.stackexchange.com/questions/93032/solving-int-infty-infty-frac14x2-sqrt4x2-space-dx), after substitution I need to calculate the new limits.

However, I do not understand why this is so:

$$\lim\_{x \to \infty}\space{\arctan(x)} = \frac{\pi}{2}$$

I tried drawing the unit circle to see what happens with $\arctan$ when $x \to \infty$ but I don't know how to draw $\arctan$. It is the inverse of $\tan$ but do you even draw $\tan$?

I would appreciate any help.