Find the area of triangle formed by tips of vectors a=i-j-3k b=4i -3j+k & c=3i-j+k.PLEASE EXPLAIN.

vectors representing the sides of the triangle will be: ab = (4-1)i + (-3+1)j + (1+3)k = 3i -2j + 4k

and ac = (3-1)i + (-1+1)j + (1+3)k = 2i + 4k

 

the area would be 1/2(ab.ac) (dot product)

it is so because the geometrical meaning of the dot product is the area of the space enclosed by the two vectors.