Question
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3tanθ + cotθ = 5cosecθ. Solve for θ, 0≤θ≤90.
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Answer: Option A
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3sinθcosθ + cosθsinθ = 5sinθ
3sin2θ + cos2θsinθcosθ=5sinθ
3sin2θ+cos2θ=5cosθ
3(1 - cos2θ) + cos2θ = 5 cosθ
2cos2θ + 5cosθ - 3 = 0
2cosθ [cosθ + 3] - 1(cosθ + 3) = 0
(cosθ + 3) (2cosθ - 1) = 0
cosθ = -3 or cosθ = 12
Note that cosθ = -3 is not possible as −1≤cosθ≤1
Thus, θ = 60∘
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