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Question

If k1=tan27θtanθ and k2=sinθcos3θ+sin3θcos9θ+sin9θcos27θ, then k1k2 is:

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Solution

Consider tan3θtanθ=sin3θcos3θsinθcosθ=sin2θcos3θcosθ=2sinθcos3θ
Similarly, tan9θtan3θ=2sin3θcos9θ
and tan27θtan9θ=2sin9θcos27θ
sinθcos3θ+sin3θcos9θ+sin9θcos27θ=12(tan27θtanθ)
k2=12k1k1=2k2k1k2=2

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