Question

If the arc length of a sector in the unit circle is 4.2, what is the measure of the angle of the sector?

Answer 1

Bear in mind the Unit Circle is called so, because its radius is exactly 1, thus just 1 unit, the Unit Circle

anyway    $\bf \theta=\cfrac{180s}{\pi r}\qquad \begin{cases} \theta=\textit{central angle in degrees}\\ r=radius\\ s=\textit{length of the arc}\\ ----------\\ s=4.2\\ r=1 \end{cases}\implies \theta=\cfrac{180\cdot 4.2}{1\cdot \pi }$