CEE Kerala Engineering CEE Kerala Engineering Solved Paper-2009

  • question_answer
    If\[f(x)=\left\{ \begin{matrix}    \frac{3\sin \pi x}{5x} & ,x\ne 0  \\    2k & ,x=0  \\ \end{matrix} \right.\]is continuous at\[x=0,\]then the value of k is equal to

    A)  \[\frac{3\pi }{10}\]                         

    B)         \[\frac{3\pi }{5}\]

    C)  \[\frac{\pi }{10}\]                           

    D)         \[\frac{3\pi }{2}\]

    E)  \[\frac{2\pi }{3}\]

    Correct Answer: A

    Solution :

    Given, \[f(x)=\left\{ \begin{matrix}    \frac{3\sin \pi x}{5x}, & x\ne 0  \\    2k, & x=0  \\ \end{matrix} \right.\] \[\therefore \]  \[LHL=\underset{x\to 0}{\mathop{\lim }}\,\frac{3\sin \pi x}{5x}\]                 \[=\underset{x\to 0}{\mathop{\lim }}\,\frac{3}{5}.\frac{\sin \pi x}{\pi x}.\pi \]                 \[=\frac{3\pi }{5}\] Also, \[f(0)=2k\] Since, \[f(x)\]is continuous at\[x=0,\]then \[f(0)=LHL\] \[\Rightarrow \]               \[2k=\frac{3\pi }{5}\Rightarrow k=\frac{3\pi }{10}\]        


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