Question

Which of the following represents direction cosines of the line :

(a)`0,1/sqrt2,1/2`

(b)`0,-sqrt3/2,1/sqrt2`

(c)`0,sqrt3/2,1/2`

(d)`1/2,1/2,1/2`

Answer 1

Ans. (C)

`l^2+m^2+n^2`

`=(0)^2+(sqrt3/2)^2+(1/2)^2`

`=3/4+1/4=1`