Step-by-step explanation:
Let us Assume A(x1, y1) = (0, 0)
Let us Assume B(x2, y2) = (1, 2)
Let us Assume C(x3, y3) = (4, 3)
Let us Assume D(x4, y4) = (3, -1)
Let us join Ac to from two triangles ∆ABC and ∆ACD
Now,
area of triangle,
= 1/2 [x1(y2−y3)+x2(y3−y1)+x3(y1−y2)]
= 1/2 [ 0(2 - 3) + 1(3 - 0) + 4(0 - 2) ]
= 1/2 [ 0 + 3 - 8 ]
= 1/2 [ -5 ]
= -5/2
same solve for second triangle and add both answer lol