Question

If A(1, 2, -3) and B(-1, -2, 1) are the end points of a vector AB then the direction cosines of AB are

A. -2, -4, 4

B. -1/2, -1, 1

C. -1/3, -2/3, 2/3

D. none of these

Answer 1

Answer is : C. -1/3, -2/3, 2/3

Given - A(1, 2, -3) and B(-1, -2, 1) are the end points of a vector AB

Tip – If P(a₁,b₁,c₁) and Q(a₂,b₂,c₂) be two points then the vector PQ is represented by

Formula to be used – The direction cosines of a vector ai+ bj + ck is given by

Hence, the direction cosines of the vector -2i - 4j + 4k is given by