MCQ
The solution of the equation $\sec \theta - {\rm{cosec}}\theta = \frac{4}{3}$ is
  • $\frac{1}{2}[n\pi + {( - 1)^n}{\sin ^{ - 1}}(3/4)]$
  • B
    $n\pi + {( - 1)^n}{\sin ^{ - 1}}(3/4)$
  • C
    $\frac{{n\pi }}{2} + {( - 1)^n}{\sin ^{ - 1}}(3/4)$
  • D
    None of these

Answer

Correct option: A.
$\frac{1}{2}[n\pi + {( - 1)^n}{\sin ^{ - 1}}(3/4)]$
a
(a) $3(\sin \theta - \cos \theta ) = 4\sin \theta \cos \theta $

==> $3(\sin \theta - \cos \theta ) = 2\sin 2\theta $

Squaring both sides, we get $9(1 - S) = 4{S^2},$

where $S = \sin 2\theta $ or $4{S^2} + 9S - 9 = 0$.

$\therefore $ $\,(S + 3)\,(4S - 3) = 0$ or $S = \frac{3}{4}$ as $S \ne - 3$

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

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

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

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