A line makes the same angle θ, with each of the x and z-axis. If the angle β , which it makes the y-axis, is such that sin2β=3sin2θ , then cos2θ equals

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answer is A.

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Detailed Solution

Here l=cosθ,m=cosβ,n=cosθ Now l2+m2n2=1⇒2cos2θ+cos2β=1 ⇒2cos2θ=sin2β Given: sin2β=3sin2θ⇒2cos2θ=3sin2θ ⇒5cos2θ=3

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