Find the area of the shaded region in figure, if radii of the two concentric circles with centre O are 7 cm and 14 cm respectively and \( ∠ \ AOC \ = \ 40° \)

Area of the shaded region

= Area of sector AOC - Area of sector OBD

\( = \ \frac{40}{360} \ × \ \pi \ × \ 14^2 \ - \ \frac{40}{360} \ × \ \pi \ × \ 7^2 \)

\( = \ \frac{1}{9} \ × \ \frac{22}{7}(196 \ - \ 49) \) \(= \ \frac{22}{63} \ × \ 147 \ = \ \frac{154}{3} \)cm²