Area of triangle having angular points (x1,y1)(x2,y2)(x3,y3) is given by the formula
△=12|x1y2+x2y3+x3y1−x2y1−x3y2−x1y3|
or △=12|(x1−x3)y2+(x2−x1)y3+(x3−x2)y1| △=12|(am1m2−am3m1)a(m2+m3)+(am2m3−am1m2)a(m3+m1)+(am3m1−am2m3)a(m1+m2)| ⇒△=12a2|m1(m2−m3)(m2+m3)+m2(m3−m1)(m3+m1)+m3(m1−m2)(m1+m2)|