what is the formula of triangle in coordinate geometry?
If area of triangle with vertices P(x1, y1), Q(x2, y2) and R(x3, y3) is zero, then (1/2) [x1 (y2- y3 )+x2 (y3-y1 )+x3(y1-y2)] = 0 and the points P(x1, y1), Q(x2, y2) and R(x3, y3)are collinear.