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A line has direction ratios 2, -1, -2. One set of its direction cosines is:
A2/3, -1/3, -2/3
B1/3, -1/3, -2/3
C2/9, -1/9, -2/9
D2, -1, -2
Answer & Solution
Correct answer: A. 2/3, -1/3, -2/3
The root of 4 + 1 + 4 is 3, so dividing each ratio by 3 gives unit-length cosines.
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