The direction cosines of a line whose direction ratios are $2,-1,2$ are:
- $2, -1, 2$
- $\tfrac12, -\tfrac11, \tfrac12$
- $\tfrac29, -\tfrac19, \tfrac29$
- $\tfrac23, -\tfrac13, \tfrac23$
Show answer and solution
Correct answer: D. $\tfrac23, -\tfrac13, \tfrac23$
Divide by √(2²+1²+2²)=3: direction cosines are (2/3, −1/3, 2/3).