JEE Main & Advanced Mathematics Limits, Continuity and Differentiability Question Bank Self Evaluation Test - Continuity and Differentiability

  • question_answer
    Which of the following functions have finite number of points of discontinuity? (where \[[\cdot ]\]represents greatest integer functions)

    A) \[tan\,x\]

    B) \[x\text{  }\!\![\!\!\text{ }x]\]

    C) \[\frac{\left| x \right|}{x}\]

    D) \[\sin \,[n\pi x]\]

    Correct Answer: C

    Solution :

    [c] \[f(x)=\tan \,\,x\] is discontinuous when \[x=(2n+1)\pi /2,n\in I\] \[f(x)=x[x]\] is discontinuous when \[x=k,k\in I\] \[f(x)=\sin [n\pi x]\] is discontinuous when \[n\pi x=k,k\in I\] Thus, all the above functions have infinite number of points of discontinuity. But \[f(x)=\frac{\left| x \right|}{x}\] is discontinuous when \[x=0\] only.


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