1. The term \textbf{arctan} refers to the \textbf{inverse tangent function}.\n\n2. It is denoted as $\arctan(x)$ and it gives the angle whose tangent is $x$.\n\n3. More formally, if $y = \arctan(x)$, then $\tan(y) = x$ and $y$ is in the interval $\left(-\frac{\pi}{2}, \frac{\pi}{2}\right)$.\n\n4. This function is useful for finding angles when you know the ratio of the opposite side to the adjacent side in a right triangle.\n\n5. For example, if $\tan(\theta) = 1$, then $\theta = \arctan(1) = \frac{\pi}{4}$.