Respuesta :

[tex]\bf \textit{arc's length}\\\\ s=r\theta \quad \begin{cases} r=radius\\ \theta =angle~in\\ \qquad radians\\ ------\\ r=40\\ \theta =\frac{1}{8} \end{cases}\implies s=40\cdot \cfrac{1}{8}\implies s=5[/tex]