we know the semi-circle has a radius of 5, and of course the central angle wil be π.
[tex]\textit{arc's length}\\\\ s=r\theta ~~ \begin{cases} r=radius\\ \theta =\stackrel{radians}{angle}\\[-0.5em] \hrulefill\\ \theta =\pi \\ r=5 \end{cases}\implies s=5\pi \implies \stackrel{\pi =3.14}{s=15.7}[/tex]
