(ii)
If area is given, use both positive and negative values of the determinant for
calculation (iii)
The area of the triangle formed by three collinear points is zero Example 6 Find the area of the triangle whose vertices are (3, 8), (– 4, 2) and (5, 1) Solution The area of triangle is given by
∆ =
3
8
1
1
4
2
1
2
5
1
1
–
Rationalised 2023-24
DETERMINANTS     83
=
(
)
(
)
(
)
1 3 2 –1 – 8 –4 – 5
1 –4 –10
2 
+



 
=
(
)
1
61
3
72
14
2
2
–
+
=
Example 7 Find the equation of the line joining A(1, 3) and B (0, 0) using determinants
and find k if D(k, 0) is a point such that area of triangle ABD is 3sq units