[填空题]
Points A and B lie on a circle with centrxv zdkojbb xh5bfq gqx:4k1n e8/- wmp1u63+ .(iaqe4k*:mzi e O and radius $6 \mathrm{~cm}$ . Suppose the angle $\theta=A \widehat{O} B$ is increasing at a rate of 0.5 radians per second.
Find the rate at which the area of the shaded region is increasing with respect to time, at the instant $\theta=2 $ radians.
the shaded area is increasing at a rate of cm$^2$/sec
