Practicing Success
If $7 \sin ^2 \theta-\cos ^2 \theta+2 \sin \theta=2,0^{\circ}<\theta<90^{\circ}$, then the value of $\frac{\sec 2 \theta+\cot 2 \theta}{{cosec} 2 \theta+\tan 2 \theta}$ is : |
$\frac{2 \sqrt{3}+1}{3}$ $\frac{1}{5}(1+2 \sqrt{3})$ $\frac{2}{5}(1+\sqrt{3})$ 1 |
$\frac{1}{5}(1+2 \sqrt{3})$ |
7 sin²θ - cos²θ + 2sinθ = 2 { sin²θ + cos²θ = 1 } 7 sin²θ - ( 1 - sin²θ ) + 2sinθ = 2 7 sin²θ + sin²θ + 2sinθ - 3 = 0 8 sin²θ + 2sinθ - 3 = 0 8 sin²θ + 6sinθ - 4sinθ - 3 = 0 2 sinθ (4sinθ + 3 ) - 1 ( 4sinθ + 3 ) = 0 (2sinθ - 1 ).( 4sinθ + 3 ) = 0 Either (2sinθ - 1 ) = 0 or ( 4sinθ + 3 ) = 0 ( 4sinθ + 3 ) = 0 is not possible. So, (2sinθ - 1 ) = 0 sinθ = \(\frac{1}{2}\) { sin 30º = \(\frac{1}{2}\) } Now, \(\frac{sec2θ + cot2θ}{cosec2θ + tan2θ}\) = \(\frac{sec60º + cot60º}{cosec60º + tan60º}\) = \(\frac{2 + 1/√3}{√3/2 + √3}\) = \(\frac{2√3 + 1}{3+ 2}\) = \(\frac{2√3 + 1}{5}\)
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