Trigonometrical Equations
hard

समीकरण $\sec \theta  - {\rm{cosec}}\theta  = \frac{4}{3}$ का व्यापक हल है

A

$\frac{1}{2}[n\pi + {( - 1)^n}{\sin ^{ - 1}}(3/4)]$

B

$n\pi + {( - 1)^n}{\sin ^{ - 1}}(3/4)$

C

$\frac{{n\pi }}{2} + {( - 1)^n}{\sin ^{ - 1}}(3/4)$

D

इनमें से कोई नहीं

Solution

$3(\sin \theta  – \cos \theta ) = 4\sin \theta \cos \theta $

$3(\sin \theta  – \cos \theta ) = 2\sin 2\theta $

दोनों पक्षों का वर्ग करने पर, $9(1 – S) = 4{S^2},$       

 जहाँ $S = \sin 2\theta $ या $4{S^2} + 9S – 9 = 0$.

$\therefore $  $\,(S + 3)\,(4S – 3) = 0$ या $S = \frac{3}{4}$,  चूँकि $S \ne  – 3$

या $\sin 2\theta  = \frac{3}{4} = \sin \alpha $

$\therefore $ $2\theta  = n\pi  + {( – 1)^n}\alpha $

या $\theta  = \frac{1}{2}\,\left[ {n\pi  + {{( – 1)}^n}{{\sin }^{ – 1}}\left( {\frac{3}{4}} \right)} \right]$.

Standard 11
Mathematics

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