# How do you evaluate arctan(1/2)?

The $\arctan \left(\frac{1}{2}\right)$ is the angle $\theta$ such that $\tan \left(\theta\right) = \frac{1}{2}$
We can imagine such an angle in the first quadrant as being part of a right-triangle with opposite side $= 1$, adjacent side $= 2$, and hypotenuse $= \sqrt{5}$.
$\arctan \left(\frac{1}{2}\right) = 0.463648 \text{ radians} = {26.56505}^{\circ}$