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\includegraphics[max width=\textwidth, alt={}, center]{fa90db86-a73a-40db-b416-3c9f470fa207-3_446_645_258_751} The diagram shows a metal plate made by removing a segment from a circle with centre \(O\) and radius 8 cm . The line \(A B\) is a chord of the circle and angle \(A O B = 2.4\) radians. Find

1. the length of \(A B\),
2. the perimeter of the plate,
3. the area of the plate.