If DEF is the triangle formed by joining the mid-points of sides of the triangle ABC, then the area of triangle ABC is 4 times the area of triangle DEF.
So find the area of triangle DEF first and multiply with 4 to get the area of ABC.
Area of a triangle with vertices (x₁,y₁); (x₂,y₂) and (x₃,y₃) is given by
Area = [ x₁(y₂ - y₃) + x₂(y₃ - y₁) + x₃(y₁ - y₂) ] / 2
Vertices of DEF are
So Area of triangle DEF
So area of DEF is
So area of ABC =