[填空题]
The following diagram fr a9cl2bvbd3 l+c..r(;gc*c0weqzo7mx4 t cc 5o0nii; mo+qshows a circle with centre O and radius 5 cm.
Points $ \mathrm{A}$,$ \mathrm{B} $ lie on the circle and $ \mathrm{AO} \mathrm{B}=2.1 $ radians.
1. Find the length of:
1. minor arc A B ; cm
2. chord A B .≈ cm
2. Find the area of the shaded region.≈ $cm ^2$
