[填空题]
The following diagram 3n4. okiwm.c1r9 goc zshows a circle with centre O v(asv(ay6- n /lc0njt3lj)xwand radius r cm.The circle is divided into three eqyvl-jwt/( a 0 6)c3v( xlnsjanual 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
