alleryA line makes equal angles with the three coordinate axes. Its direction cosines are:
A$\tfrac13, \tfrac13, \tfrac13$
B$1, 1, 1$
C$\tfrac1{\sqrt3}, \tfrac1{\sqrt3}, \tfrac1{\sqrt3}$
D$\tfrac1{\sqrt2}, \tfrac1{\sqrt2}, 0$
Answer & Solution
Correct answer: C. $\tfrac1{\sqrt3}, \tfrac1{\sqrt3}, \tfrac1{\sqrt3}$
Equal angles ⟹ l=m=n and l²+m²+n²=1 ⟹ 3l²=1 ⟹ l=1/√3 for each.
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