JEE Main & Advanced Mathematics Relations Question Bank Mock Test - Relations and Functions

  • question_answer
    The range of the function f defined by \[f(x)=\left[ \frac{1}{\sin \left\{ x \right\}} \right]\] (where [.] and \[\left\{ . \right\}\], respectively, denote the greatest integer and the fractional part functions) is

    A) I, the set of integers

    B) N, the set of natural numbers

    C) W, the set of whole numbers

    D) \[\left\{ 1,2,3,4.... \right\}\]

    Correct Answer: D

    Solution :

    [d] Since \[\{x\}\in [0,\,\,1),sin\{x\}\in (0,\,\,sin1)\] as \[f(x)\] is defined if \[\sin \{x\}\ne 0,\] i.e., \[\frac{1}{\sin \{x\}}\in \left( \frac{1}{\sin 1},\infty  \right)\] Or \[\left[ \frac{1}{\sin \{x\}} \right]\in \{1,2,3...\}\] Note that \[1<\frac{\pi }{3}\] or \[\sin 1<\sin \frac{\pi }{3}=0.866\] or \[\frac{1}{\sin 1}>1.155.\]


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