Answer
$s=r\displaystyle \theta\cdot\frac{180^{\mathrm{o}}}{\pi}$
Work Step by Step
Converting between Degrees and Radians
1. Multiply a degree measure by $\displaystyle \frac{\pi}{180}$ radian and simplify to convert to radians.
2. Multiply a radian measure by $\displaystyle \frac{180^{\mathrm{o}}}{\pi}$ and simplify to convert to degrees.
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Since $\theta$ is in radians (and we want degrees), we apply case 2.
$s=r\displaystyle \theta\cdot\frac{180^{\mathrm{o}}}{\pi}$
