Practicing Success
If $12 \cos^2 \theta - 2 \sin^2 \theta + 3\cos \theta = 3, 0^\circ < \theta < 90^\circ$, then what is the value of $\frac{cosec~\theta + \sec \theta}{\tan \theta + \cot \theta}$? |
$\frac{4 + \sqrt{3}}{4}$ $\frac{1 + 2\sqrt{2}}{2}$ $\frac{1 + \sqrt{3}}{2}$ $\frac{2 + \sqrt{3}}{4}$ |
$\frac{1 + \sqrt{3}}{2}$ |
12 cos²θ - 2sin²θ + 3cosθ = 3 12 cos²θ - 2 ( 1 - cos²θ ) + 3cosθ = 3 14 cos²θ + 3cosθ - 5 = 0 14 cos²θ + 10cosθ -7cosθ - 5 = 0 2cosθ ( 7cosθ + 5 ) - 1 ( 7cosθ + 5 ) = 0 ( 2cosθ - 1 ) . ( 7cosθ + 5 ) = 0 Either ( 2cosθ - 1 ) = 0 Or ( 7cosθ + 5 ) = 0 ( 7cosθ + 5 ) = 0 cosθ = - \(\frac{5}{7}\) ( not possible ) So, ( 2cosθ - 1 ) = 0 cosθ = \(\frac{1}{2}\) { we know, cos60º = \(\frac{1}{2}\) } So , θ = 60º Now, \(\frac{cosecθ+ secθ }{tanθ + cotθ}\) = \(\frac{cosec60º+ sec60º }{tan60º + cot60º}\) = \(\frac{2/√3 +2 }{√3 + 1/√3}\) = \(\frac{2√3 +2 }{4}\) = \(\frac{√3 +1 }{2}\)
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