SSC CGL 2023 PYQ — Question 59

SSC CGL - 21 July 2023 - Shift 3 • Quantitative Aptitude • Q59

 Simplify the following expression. sinθ−2sin3θ2cos3θ−cosθ\frac{sin\theta- 2sin^3\theta}{ 2 cos^3\theta -cos\theta }

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Correct answer: A

Explanation

The correct answer is option 1 i.e. tanθ\theta 
sinθ−2sin3θ2cos3θ−cosθ\frac{sin\theta- 2sin^3\theta}{ 2 cos^3\theta -cos\theta }

⇒ sinθ(1−2sin2θ)cosθ(2cos2θ−1)\frac{sinθ(1−2sin^2θ)}{cosθ(2cos^2θ−1)}

the terms 1 − 2sin⁡2θ and 2cos⁡2θ − 1 are the same because of the Pythagorean identity:

⇒ sin⁡2θ + cos⁡2θ = 1

Thus, 1 − 2sin⁡2θ = 2cos⁡2θ − 1

So, sin⁡θ/cos⁡θ = tanθ