[填空题]
The following diagraw7zj/ +fojido1 9-gqpm shows a cg 3* znfqhrri3.:- gvjpbcq,c z:4 c1circle with centre O and radius r cm.The circle is divided into4-* czr3c vg1:,jqh.cpb nfgq3r :izc three equal sectors.
Points $\mathrm{A}, \mathrm{B}$ lie on the circle and $\mathrm{AO} \mathrm{B}=\theta$ radians.
1. Find the exact value of $\theta$ , giving your answer in terms of $\pi$ .
The area of the shaded sector $\mathrm{AOB} $ is $ 3 \pi \mathrm{cm}^{2}$ .
2. Find the radius of the circle, r . cm
3 . Find the length of the chord A B . ≈ cm
