Instructions:[br]In the diagram, [i]O[/i] is the centre of the circle. [br][i]A[/i], [i]B[/i], [i]C[/i] and [i]D[/i] are 4 points on the circumference. [br]Angle [i]ACB[/i] and [i]ADB[/i] are subtended by the arc [i]AB[/i]. (So angle [i]ACB [/i]and angle [i]ADB[/i] must always lie on arc [i]AB)[/i][br][br]Move points [i]A[/i], [i]B[/i], [i]C[/i] and [i]D[/i] around.