Answer
(a) $4\pi$
(b) $\frac{2\pi}{3}$
Work Step by Step
(a) One rotation is completed in 12 hours. So, in 24 hr, 2 rotations are completed.
2 rotations=$2\,rotations\times\frac{2\pi\,radians}{1\,rotation}=4\pi\,radians$
(b) In 12 hours, one rotation is completed. This implies that $\frac{4}{12}=\frac{1}{3}$ rotation is completed in 4 hours.
As 1 rotation is equal to $2\pi$ radians, $\frac{1}{3}$ rotation is equal to $\frac{1}{3}\times2\pi=\frac{2\pi}{3}$ radians.
