Answer the following in the context of the area of a triangle formed by three points in the plane.
(i) State the formula for twice the area of a triangle whose vertices are (x1,y1), (x2,y2) and (x3,y3) in terms of their coordinates.
(ii) Explain, with reasoning, why the three points are collinear whenever this area becomes zero.
(iii) Using your explanation in part (ii), verify that the points P(1,2), Q(4,6) and R(7,10) are collinear.