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A line makes angles α, β, γ, δ with the four diagonals of a unit cube. 

cos 2α + cos 2β + cos 2γ + cos 2δ is

(a) 1/3 

(b) 4/3 

(c) –8/3 

(d) –4/3

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Answer is (d) –4/3

cos 2α + cos 2β + cos 2γ + cos 2δ

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