r = 15
The circumference of circle: \(C=2\pi r\)
subtitute: \(C=2\pi\cdot15=30\pi\)
\(1\ rad=\dfrac{180^o}{\pi}\to5\ rad=5\cdot\dfrac{180^o}{\pi}=\dfrac{900^o}{\pi}\)
\(\dfrac{5\ rad}{360^o}=\dfrac{\frac{900^o}{\pi}}{360^o}=\dfrac{900^o}{\pi}\cdot\dfrac{1}{360^o}=\dfrac{5}{2\pi}\)
\(s=\dfrac{5}{2\pi}C\to s=\dfrac{5}{2\pi}\cdot30\pi=75\)
Answer: C. s = 75
