JCECE Engineering JCECE Engineering Solved Paper-2007

  • question_answer
    \[\underset{x\to \frac{\pi }{6}}{\mathop{\lim }}\,\frac{\sin 2x}{\sin x}\]is equal to

    A) \[\sqrt{3}\]                                        

    B) \[\frac{1}{\sqrt{3}}\]

    C) \[2\]                                     

    D) \[\frac{1}{2}\]

    Correct Answer: A

    Solution :

    \[\underset{x\to \frac{\pi }{6}}{\mathop{\lim }}\,\frac{\sin 2x}{\sin x}=\underset{x\to \frac{\pi }{6}}{\mathop{\lim }}\,\frac{2\sin x\cos x}{\sin x}\]                 \[=2\lim \cos x\]                 \[=2\frac{\sqrt{3}}{2}=\sqrt{3}\] Alternate Method: \[\underset{x\to \frac{\pi }{6}}{\mathop{\lim }}\,\frac{\sin 2x}{\sin x}=\frac{\sin 2\frac{\pi }{6}}{\sin \frac{\pi }{6}}=\frac{\sqrt{3}/2}{1/2}=\sqrt{3}\]


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