Activity:[br]In the figure, two sectors [i]OAB[/i] and [i]OCD[/i] are of different sizes. Observe the sizes of the subtended angles, the lengths of the corresponding arcs and chords. [br][br]1. Find the relation(s) between the angles at centre, lengths of arcs and lengths of chords.  [br]2. Prove the above relation mathematically.