Question

The direction cosines of the vector `3hati-4hatj+5hatk` are
A. `(3)/(5),-(4)/(5),(1)/(5)`
B. `(3)/(5sqrt(2)),(-4)/(5sqrt(2)),(1)/(sqrt(2))`
C. `(3)/(sqrt(2)),(-4)/(sqrt(2)),(1)/(sqrt(2))`
D. `(3)/(5sqrt(2)),(4)/(5sqrt(2)),(1)/(sqrt(2))`.

Answer 1

Correct Answer - B
Vector `A=3hati-4hatj+5hatk`, we know that, direction cosines of
`A=(3)/(sqrt(3^(2)+4^(2)+5^(2))),(-4)/(sqrt(3^(2)+4^(2)+5^(2))),(5)/(sqrt(3^(2)+4^(2)+5^(2)))`
`=(3)/(5sqrt(2)),(-4)/(5sqrt(2)),(1)/(sqrt(2))`