JEE Main & Advanced Mathematics Trigonometric Equations Question Bank Solution of trigonometrical equations

  • question_answer
    The general value of \[\theta \] satisfying \[{{\sin }^{2}}\theta +\sin \theta =2\] is [AMU 1996, 99]

    A) \[n\pi +{{(-1)}^{n}}\frac{\pi }{6}\]

    B) \[2n\pi +\frac{\pi }{4}\]

    C) \[n\pi +{{(-1)}^{n}}\frac{\pi }{2}\]

    D) \[n\pi +{{(-1)}^{n}}\frac{\pi }{3}\]

    Correct Answer: B

    Solution :

    \[{{\sin }^{2}}\theta +\sin \theta -2=0\Rightarrow (\sin \theta -1)\,(\sin \theta +2)=0\] \[\Rightarrow \] \[\sin \theta \ne -2\] ,  \[\therefore \,\,\sin \theta =1=\sin \pi /2\] \[\Rightarrow \] \[\theta =n\pi +{{(-1)}^{n}}\frac{\pi }{2}\].


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