Let O be the centre of a circle of radius r centimetres, and let P be a point outside the circle such that OP = d centimetres (d > r). Two tangents PT and PS are drawn from P to the circle.
(i) Show that PT2=d2−r2.
(ii) Derive an expression for the area of the quadrilateral OPTS in terms of r and d.
(iii) Using your expression, find the area of quadrilateral OPTS when r = 5 cm and d = 13 cm.