Respuesta :

[tex]\bf \textit{arc's length}\\\\ s=r\theta \qquad \begin{cases} r=radius\\ \theta =angle~in\\ \qquad radians\\ ------\\ r=5\\ \theta =\frac{4\pi }{7} \end{cases}\implies s=5\cdot \cfrac{4\pi }{7}[/tex]