Manipal Engineering Manipal Engineering Solved Paper-2012

  • question_answer
    If\[\frac{\pi }{2}<\theta <\frac{3\pi }{2}\], then the value of\[\sqrt{\frac{1-\sin \theta }{1+\sin \theta }}\]is equal to

    A) \[-\sec \theta +\tan \theta \]    

    B) \[\sec \theta +\tan \theta \]

    C) \[\sec \theta -\tan \theta \]   

    D)                         None of these

    Correct Answer: A

    Solution :

    \[\sqrt{\frac{1-\sin \theta }{1+\sin \theta }}=\sqrt{\frac{{{(1-\sin \theta )}^{2}}}{1-{{\sin }^{2}}\theta }}\]                     \[=\frac{1-\sin \theta }{\sqrt{{{\cos }^{2}}\theta }}=\frac{1-\sin \theta }{|\cos \theta |}\]                     \[=\frac{1-\sin \theta }{-\cos \theta }\]              \[\left( \because \,\,\frac{\pi }{2}<\theta <\frac{3\pi }{2} \right)\]                    \[=-\frac{1}{\cos \theta }+\frac{\sin \theta }{\cos \theta }\]                      \[=-\sec \theta +\tan \theta \]


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