Trigonometrical Equations
hard

समीकरण $(\sqrt 3  - 1)\sin \theta  + (\sqrt 3  + 1)\cos \theta  = 2$ का व्यापक हल है

A

$2n\pi \pm \frac{\pi }{4} + \frac{\pi }{{12}}$

B

$n\pi + {( - 1)^n}\frac{\pi }{4} + \frac{\pi }{{12}}$

C

$2n\pi \pm \frac{\pi }{4} - \frac{\pi }{{12}}$

D

$n\pi + {( - 1)^n}\frac{\pi }{4} - \frac{\pi }{{12}}$

Solution

माना $\sqrt 3  + 1 = r\cos \alpha $ तथा $\sqrt 3  – 1 = r\sin \alpha $.

तब  $r = \sqrt {{{(\sqrt 3  + 1)}^2} + {{(\sqrt 3  – 1)}^2}}  = 2\sqrt 2 $

$tan\alpha  = \frac{{\sqrt 3  – 1}}{{\sqrt 3  + 1}} = \frac{{1 – (1/\sqrt 3 )}}{{1 + (1/\sqrt 3 )}} = \tan \left( {\frac{\pi }{4} – \frac{\pi }{6}} \right) $

$\Rightarrow \alpha  = \frac{\pi }{{12}}$

दिये गये समीकरण को लिखा जा सकता है

$2\sqrt 2 \cos (\theta  – \alpha ) = 2 $

$\Rightarrow \cos \left( {\theta  – \frac{\pi }{{12}}} \right) = \cos \frac{\pi }{4}$

$ \Rightarrow $ $\theta  – \frac{\pi }{{12}} = 2n\pi  \pm \frac{\pi }{4} $

$\Rightarrow \theta  = 2n\pi  \pm \frac{\pi }{4} + \frac{\pi }{{12}}$.

Standard 11
Mathematics

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