[填空题]
The following diagram sho kn z5br0rn 94kj9)kxvws nyw9k7awb x, 2part of a circle with centre O and radius 5 cm.
Points $\mathrm{A}, \mathrm{B}$ lie on the circle, chord $\mathrm{AB}$ has a length of 8 $\mathrm{~cm}$ and $\mathrm{AO} \mathrm{B}=\theta$ .
1. Find the value of $ \theta$ , giving your answer in radians.≈
2. Find the area of the shaded region.≈ $cm ^2$
