JEE Main & Advanced AIEEE Solved Paper-2013

  • question_answer
    \[\underset{x\to 0}{\mathop{\lim }}\,\frac{(1-\cos 2x)(3+\cos x)}{x\tan 4x}\]is equal to:     AIEEE Solevd Paper-2013

    A) \[-\frac{1}{4}\]                                 

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

    C)        1                             

    D)        2

    Correct Answer: D

    Solution :

    \[\underset{x\to 0}{\mathop{\lim }}\,\frac{(1-\cos 2x)(3+\cos x)}{x\tan 4x}\] \[=\underset{x\to 0}{\mathop{\lim }}\,\frac{(2si{{n}^{2}}x)(3+\cos x)}{x\left( \frac{\tan 4x}{4x} \right)\times 4x}\] \[=\underset{x\to 0}{\mathop{\lim }}\,\frac{2{{\sin }^{2}}x(3+\cos x)}{4{{x}^{2}}}=\frac{2}{4}(3+1)=2\]


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