Using vectors, find the area of the triangle ABC with vertices A(1, 2, 3), B(2, – 1, 4) and C(4, 5, – 1).


We have,


The coordinates of points A, B and C are (1, 2, 3), (2, -1, 4) and (4, 5, -1) respectively.


We need to find the area of this triangle ABC.


We have the formula given as,


…(i)


Let us find out and first.


We can say,


Position vector of A



Position vector of B



Position vector of C



For :


Position vector of B-Position vector of A






For :


Position vector of C-Position vector of A






Now, substitute values of and in . We can find out as,






And,






From equation (i), we get





Thus, area of ∆ABC is .


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