SSC CHSL 2024 PYQ — Question 75

SSC CHSL - 03 July 2024 - Shift 3 • Quantitative Aptitude • Q75

3cos⁡3θ−2cos⁡θsin⁡θ−3sin⁡3θ\frac{3 \cos^3 \theta - 2 \cos \theta}{\sin \theta - 3 \sin^3 \theta} is equal to:

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Correct answer: C

Explanation

The correct answer is option 3 i.e. cot θ.

⇒ 3cos⁡3θ−2cos⁡θsin⁡θ−3sin⁡3θ\frac{3 \cos^3 \theta - 2 \cos \theta}{\sin \theta - 3 \sin^3 \theta}

⇒ [cos θ(3cos2θ - 2)]/[sin θ(1 - 3sin2θ)]

We know,

cos2θ = 1 - sin2θ

⇒ [cos θ(3(1 - sin2θ) - 2)]/[sin θ(1 - 3sin2θ)]

⇒ [cos θ(1 - 3sin2θ)]/[sin θ(1 - 3sin2θ)]

⇒ cos θ/sin θ = cot θ