[b]Check boxes for the following:[/b][br]1. Hint for (a): Through different stages[br][br][b]Blue dots for :[/b][br]1. Rotation of points or translation of circle.[br][br][b]Question:[/b][br]The diagram shows a circle of centre o, with radius r metres. A and D are points on the circle such that AD = 16 cm.[br]E is the midpoint of AD and E is on OF such that EF = x metres.[br][br](a) Show that [math]x^2 - 2rx + 64 = 0[/math][br](b) Express r in terms of x.[br](c) Hence, given then EF = 4 cm, calculate the radius of of the sphere.