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In the diagram, \(O A B\) and \(O C D\) are radii of a circle, centre \(O\) and radius 16 cm . Angle \(A O C = \alpha\) radians. \(A C\) and \(B D\) are arcs of circles, centre \(O\) and radii 10 cm and 16 cm respectively.
- In the case where \(\alpha = 0.8\), find the area of the shaded region.
- Find the value of \(\alpha\) for which the perimeter of the shaded region is 28.9 cm .