JCECE Engineering JCECE Engineering Solved Paper-2007

  • question_answer
    \[\underset{x\to \infty }{\mathop{\lim }}\,\sqrt{\frac{x-\sin x}{x+{{\cos }^{2}}x}}\]is equal to

    A) \[-1\]                                    

    B) \[0\]

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

    D) \[1\]

    Correct Answer: D

    Solution :

    Key Idea:                 \[\underset{x\to \infty }{\mathop{\lim }}\,\frac{\sin x}{x}=0,\,\,\underset{x\to \infty }{\mathop{\lim }}\,\frac{\cos x}{x}=0\] Let          \[A=\underset{x\to \infty }{\mathop{\lim }}\,\sqrt{\frac{x-\sin x}{x+{{\cos }^{2}}x}}\] \[\Rightarrow \]               \[A=\underset{x\to \infty }{\mathop{\lim }}\,\sqrt{\frac{1-\frac{\sin x}{x}}{1+\frac{{{\cos }^{2}}x}{x}}}\] \[\Rightarrow \]               \[A=\sqrt{\frac{1-0}{1+0}}=1\]


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