JEE Main & Advanced Mathematics Trigonometric Identities Question Bank Fundamental trigonometrical ratios and functions, Trigonometrical ratio of allied angles

  • question_answer
    If \[\pi <\alpha <\frac{3\pi }{2}\], then \[\sqrt{\frac{1-\cos \alpha }{1+\cos \alpha }}+\sqrt{\frac{1+\cos \alpha }{1-\cos \alpha }}\]=

    A) \[\frac{2}{\sin \alpha }\]

    B) \[-\frac{2}{\sin \alpha }\]

    C) \[\frac{1}{\sin \alpha }\]

    D) \[-\frac{1}{\sin \alpha }\]

    Correct Answer: B

    Solution :

    \[\sqrt{\frac{1-\cos \alpha }{1+\cos \alpha }}+\sqrt{\frac{1+\cos \alpha }{1-\cos \alpha }}=\frac{1-\cos \alpha +1+\cos \alpha }{\sqrt{1-{{\cos }^{2}}\alpha }}\] \[=\frac{2}{\pm \sin \alpha }\]\[=\frac{2}{-\sin \alpha },\,\,\left( \text{since }\pi <\alpha <\frac{\text{3}\pi }{\text{2}} \right).\]


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