alleryThe cosine of the angle between two lines with direction ratios $(1,2,2)$ and $(2,2,1)$ is:
A$\tfrac{4}{9}$
B$\tfrac{2}{3}$
C$\tfrac{1}{9}$
D$\tfrac{8}{9}$
Answer & Solution
Correct answer: D. $\tfrac{8}{9}$
We have cosθ = (1·2+2·2+2·1)/(√9·√9).
So cosθ = 8/9.
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