SSC CHSL 2021 PYQ — Question 70

SSC CHSL - 13 April 2021 - Shift 1 • Quantitative Aptitude • Q70

If cosecθ+cotθcosecθ−cotθ=7{{cosec\theta+cot\theta} \over cosec\theta-cot\theta}=7, then the value of 4sin2θ+54sin2θ−1{{4sin^2\theta+5} \over 4sin^2\theta-1}  is:

Show answer & explanation

Correct answer: D

Explanation

The correct answer is Option 4 i.e. 9.

Given that

cosecθ+cotθcosecθ−cotθ=7{{cosec\theta+cot\theta} \over cosec\theta-cot\theta}=7

By Componendo Dividendo Rule

(cosecθ+cotθ)+(cosecθ−cotθ)(cosecθ−cotθ)−(cosecθ+cotθ){{(cosec\theta+cot\theta)+(cosec\theta-cot\theta)} \over (cosec\theta-cot\theta) - (cosec\theta+cot\theta)} = 86\frac{8}{6}

cosecθ/cotθ = 4/3

cosθ = 3/4 

sin2θ = 7/16

Put value in given equation 

4sin2θ+54sin2θ−1{{4sin^2\theta+5} \over 4sin^2\theta-1}= 4(7/16)+54(7/16)−1{{4(7/16)+5} \over 4(7/16)-1}= 27/9 = 9