A line makes equal angles with co-ordinate axis. Direction cosines of this line are
A line makes equal angles with co-ordinate axis. Direction cosines of this line are
(A) ± (1, 1, 1)
(B) ±(1/√3, 1/√3, 1/√3)
(C) ±(1/3, 1/3, 1/3)
(D) ±(1/√3, -1/√3, -1/√3)
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(B) is the correct answer. Let the line makes angle α with each of the axis.
Then, its direction cosines are cos α, cos α, cos α.
Since cos2 α + cos2 α + cos2 α = 1. Therefore, cos α = 1/√3
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