a)
\(r=12 \text{ cm}\\
\phi=5\text{ h}=30^{\circ}=\dfrac{30\pi}{180} \text{ rad}=\dfrac{\pi}{6} \text{ rad}\\
L=12\cdot\dfrac{\pi}{6} =2\pi \text{ cm}\)
b)
\(A=\dfrac{\alpha \pi r^2}{360}\\
r=12 \text{ cm}\\
\alpha =2 \text{ h}=2\cdot30=60^{\circ}\\
A=\dfrac{60\cdot \pi \cdot 12^2}{360}\\
A=24\pi \text{ cm}^2\)
