SSC CGL 2023 PYQ — Question 65

SSC CGL - 27 July 2023 - Shift 3 • Quantitative Aptitude • Q65

If tan4 θ + tan2 θ = 1, what is the value of 11 (cos4 θ + cos2 θ)?

Show answer & explanation

Correct answer: D

Explanation

The correct answer is option 4 i.e. 11.

Tan4θ + Tan2θ = 1

⇒ Tan2θ (Tan2θ + 1) = 1

⇒ Tan2θ × Sec2θ = 1      {∵ sec2θ = 1 + tan2θ}

⇒ (sin2 θ/cos4 θ) = 1

⇒ 1 – cos2θ = cos4 θ      {∵ sin2 θ = 1 – cos2θ}

⇒ cos4 θ + cos2 θ = 1

Hence

⇒ 11(cos4 θ + cos2 θ) = 1 × 11 = 11