Practicing Success
If $7 \cos ^2 \theta+3 \sin ^2 \theta=6,0^{\circ}<\theta<90^{\circ}$, then the value of $\frac{\cot ^2 2 \theta+\sec ^2 2 \theta}{\tan ^2 2 \theta-\sin ^2 2 \theta}$ is: |
$\frac{52}{27}$ $\frac{26}{15}$ $\frac{28}{27}$ $\frac{49}{45}$ |
$\frac{52}{27}$ |
7 cos²θ + 3 sin²θ = 6 4cos²θ + 3cos²θ + 3 sin²θ = 6 { sin²θ + cos²θ = 1 } 4cos²θ = 3 cosθ= \(\frac{ √3}{2}\) { we know, cos30º= \(\frac{ √3}{2}\) } So, θ = 30º Now, \(\frac{ cot²2θ + sec²2θ}{tan²2θ- sin²2θ}\) = \(\frac{ cot²60º + sec²60º}{tan²60º- sin²60º}\) = \(\frac{ 1/3 + 4}{3- 3/4}\) = \(\frac{ 13/3}{9/4}\) = \(\frac{ 52}{27}\)
|