## Calculus (3rd Edition)

$s_1 = 3.6$ $s_2 = 8$
Recall: An angle of $\theta$ radians subtends an arc of length $\theta r$ on a circle of radius $r$ Let $s_1$ denote the length of the arc subtended by $\theta$ $$s_1 = r\theta \\[3mm] s_1 = 4 \times 0.9 \\[3mm] s_1 = 3.6$$ Let $s_2$ denote the length of the arc subtended by $\phi$ $$s_2 = r \phi \\[3mm] s_2 = 4 \times 2 \\[3mm] s_2 = 8$$