SSC CGL 2024 PYQ — Question 55

SSC CGL - 17 Sep 2024 - Shift 2 • Quantitative Aptitude • Q55

Find the value of [4cos(90−θ)sin3(90+θ)−4sin(90+θ)cos3(90−θ)cos(180+8θ2)]\bigg[{{ 4cos(90-θ)sin^3(90+θ)-4sin(90+θ)cos^3(90-θ) }\over {cos({180+8θ\over2})}} \bigg].

Show answer & explanation

Correct answer: A

Explanation

The correct answer is option 1 i.e. −1.

Given, [4cos(90−θ)sin3(90+θ)−4sin(90+θ)cos3(90−θ)cos(180+8θ2)]\bigg[{{ 4cos(90-θ)sin^3(90+θ)-4sin(90+θ)cos^3(90-θ) }\over {cos({180+8θ\over2})}} \bigg]

⇒ [4sinθcos3θ−4cosθsin3θcos(90+4θ)]\bigg[{{ 4sinθ cos^3θ-4cosθsin^3θ}\over {cos({90+4θ})}} \bigg]

⇒ [4sinθcosθ(cos2θ−sin2θ)−sin(4θ)]\bigg[{{ 4sinθ cosθ(cos^2θ - sin^2θ)}\over {-sin(4θ)}} \bigg]

⇒ [2(2sinθcosθ)(cos2θ)−sin(4θ)]\bigg[{{2(2sinθ cosθ)(cos2θ)}\over {-sin(4θ)}} \bigg]

⇒ [2(sin2θ)(cos2θ)−sin(4θ)]\bigg[{{2(sin2θ)(cos2θ)}\over {-sin(4θ)}} \bigg]

⇒ [sin4θ−sin4θ]\bigg[{{sin4θ}\over {-sin4θ}} \bigg] = -1