Consider that the length of the arc 'C', angle (in radians) of the arc 'Θ', and the radius 'R' are related as,
[tex]\theta=\frac{C}{R}[/tex]
According to the given figure,
[tex]\begin{gathered} C=2\pi \\ R=4 \end{gathered}[/tex]
So the corresponding angle can be calculated as,
[tex]\begin{gathered} \theta=\frac{2\pi}{4} \\ \theta=\frac{\pi}{2} \\ \theta\approx1.57 \end{gathered}[/tex]
Thus, the angle measures π/2 or 1.57 radians.
