Chapter 3 - Section 3.4 - Arc Length and Area of a Sector - 3.4 Problem Set - Page 155: 35

3 in

We know that the length of the arc $s$ cut off by $\theta$ can be calculated as $s=r\theta$. Therefore, we also know that $r=\frac{s}{\theta}$. We are given that $\theta=1.4$ and $s=4.2$ in. Therefore, $r=\frac{4.2}{1.4}=\frac{4.2\div1.4}{1.4\div1.4}=\frac{3}{1}=3$ in.