Question
A line AB in three-dimensional space makes angles 45° and 120° with the positive x-axis and the positive y-axis respectively. If AB makes an acute angle θ with the positive z-axis, then θ
-
30°
-
45°
-
60°
-
75°
Solution
C.
60°
cos2α +cos2β + cos2γ = 1
α = 45°,β = 120°, γ = θ