Point [i]O [/i]is the centre of the circle. You can freely move:[br]1. Point [i]C [/i]to control the size and position of the angle at circumference.[br]2. Points [i]A [/i]and [i]B [/i]to control the size and position of the angle at centre.[br][br][b][u]Exploration[/u][/b][br]By moving point [i]C[/i], explore under what situation will the angle at circumference has a special relationship with the angle at centre. Draw the two different figures obtained during the exploration.[br][br][b][u]Question[/u][/b][br]1. Suggest a relationship between angle at centre and angle at circumference sustained by the same arc.[br]2. In what way the arc length of angles sustained by the same arc affects the above relationship?[br][br]