JEE Main & Advanced Mathematics Functions Question Bank Limits

  • question_answer
     \[\underset{\theta \to 0}{\mathop{\lim }}\,\frac{\sin 3\theta -\sin \theta }{\sin \theta }=\] [AI CBSE 1984; DSSE 1984]

    A)                 1

    B)                 2

    C)                 1/3

    D)                 3/2

    Correct Answer: B

    Solution :

                       \[\underset{\theta \to 0}{\mathop{\lim }}\,\,[3-4\,{{\sin }^{2}}\theta ]-1=2.\]            Aliter : \[\underset{\theta \to 0}{\mathop{\lim }}\,\,\frac{\sin 3\theta -\sin \theta }{\sin \theta }=\underset{\theta \to 0}{\mathop{\lim }}\,\,\frac{\sin 3\theta }{\sin \theta }-\underset{\theta \to 0}{\mathop{\lim }}\,\,\frac{\sin \theta }{\sin \theta }\]                                                 \[=\frac{3}{1}-1=2.\]                                 You may also apply L-Hospital rule.


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