[填空题]
The diagram below shows a faqnbrr )1)* axenced triangular enclosure in the middle of a graspvkl9qd- . z2osy field pl.dv-k9q2 o zwhere $\mathrm{AC}=3 \mathrm{~m}, \mathrm{DC}=2 \mathrm{~m}, \mathrm{CB} \mathrm{A}=\alpha $ radians and $ \mathrm{AC} \hat{\mathrm{CB}}=\frac{\pi}{3} $ radians. One end of a rope is attached at point D on the outside edge of the enclosure, and the other end is attached to a goat G . Given that the rope is 6 $\mathrm{~m}$ long and the area of field outside the enclosure that the goat is able to graze is 74 $\mathrm{~m}^{2}$ , find the value of $\alpha$ .≈
