JEE Main & Advanced Sample Paper JEE Main Sample Paper-39

  • question_answer
    \[f(x)=\frac{\sin 3x}{\sin x},\] when \[x\ne 0\]= k,   when \[x=0\] for the function to be continuous k should be

    A)  3                                

    B)  0

    C)  -3                               

    D)  -1

    Correct Answer: A

    Solution :

     For f(x) to be continuous, \[\underset{x\to 0}{\mathop{\lim }}\,f(x)=f(0)\]\[f(0)=k\] \[\underset{x\to 0}{\mathop{\lim }}\,f(x)=\underset{x\to 0}{\mathop{\lim }}\,=\frac{\sin 3x}{\sin x}=\underset{x\to 0}{\mathop{\lim }}\,\frac{3.\frac{\sin 3x}{3x}}{\frac{\sin x}{x}}=3\]\[\left[ \because \underset{x\to 0}{\mathop{\lim }}\,\frac{\sin \theta }{\theta }=1 \right]\] \[\Rightarrow k=3\]


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