JAMIA MILLIA ISLAMIA Jamia Millia Islamia Solved Paper-2009

  • question_answer
        The general value of 6 satisfying the equation \[2si{{n}^{2}}\theta -3sin\theta -2=0\]is

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

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

    C)  \[n\pi +{{(-1)}^{n}}\frac{5\pi }{6}\]        

    D)  \[n\pi +{{(-1)}^{n}}\frac{7\pi }{6}\]

    Correct Answer: A

    Solution :

                    \[2{{\sin }^{2}}\theta -3\sin \theta -2=0\] \[\Rightarrow \]\[(2\sin \theta +1)(\sin \theta -2)=0\] \[\Rightarrow \]               \[\sin \theta =-\frac{1}{2}\]                         \[[\because \sin \theta \ne 2]\] \[\Rightarrow \]\[\sin \theta =\sin \left( -\frac{\pi }{6} \right)\Rightarrow \theta =n\pi +{{(-1)}^{n}}\left[ -\frac{\pi }{6} \right]\] \[\Rightarrow \]\[n\pi +{{(-1)}^{n+1}}\frac{\pi }{6}\]


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