If $\frac{cosec~\theta+\cot \theta}{cosec~\theta-\cot \theta}=7$, then the value of $\frac{4 \sin ^2 \theta-1}{4 \sin ^2 \theta+5}$ is: |
$-\frac{1}{9}$ $\frac{1}{3}$ $-\frac{1}{3}$ $\frac{1}{9}$ |
$\frac{1}{9}$ |
We are given that :- \(\frac{ cosecθ + cotθ}{cosecθ - cotθ }\) = 7 cosecθ + cotθ = 7cosecθ - 7cotθ 8 cotθ = 6 cosecθ cosθ = \(\frac{ 3}{4}\) Now, cos²θ = \(\frac{ 9}{16}\) { using , sin²θ + cos²θ = 1 } 1 - sin²θ = \(\frac{ 9}{16}\) sin²θ = 1 - \(\frac{ 9}{16}\) sin²θ = \(\frac{ 7}{16}\) Now, \(\frac{ 4sin²θ - 1 }{4sin²θ + 5 }\) = \(\frac{ 4 × 7/16 - 1 }{4×7/16 + 5 }\) = \(\frac{ 3/4 }{27/4 }\) = \(\frac{ 1 }{9 }\) |