Prove that the area of triangle whose vertices are (t, t – 2), (t + 2, t + 2) and (t + 3, t) is independent of t
Let A = ( x1,y1) = (t, t-2), B( x2,y2) = (t + 2, t + 2) and C = ( x3,y3) = (t + 3, t) be the vertices of the given triangle. Then,
Area of ΔABC = 12 |x1 (y2 - y3 ) + x2 (y3 - y1 ) + x3 (y1 - y2 )|
Area of ΔABC = 12 |{t(t + 2 - t) + (t + 2)(t - t + 2) + (t + 3)(t - 2 - t - 2)}|
Area of ΔABC = 12 |{2t + 2t + 4 - 4t - 12}| = |-4| = 4 sq. units
Clearly, area of ΔABC is independent of t.