JCECE Engineering JCECE Engineering Solved Paper-2013

  • question_answer
    If \[f:\left[ 0,\,\,\frac{\pi }{2} \right]\to [0,\,\,\infty ]\] be a function defined by \[y=\sin \left( \frac{x}{2} \right)\], then \[f\] is

    A)  injective                             

    B)  subjective

    C)  objective                           

    D)  None of these

    Correct Answer: D

    Solution :

    We have,                 \[y=\sin \frac{x}{2}\] and        \[0\le x\le \frac{\pi }{2}\] \[\Rightarrow \]               \[0\le \frac{x}{2}\le \frac{\pi }{4}\] \[\Rightarrow \]               \[0\le \sin \frac{x}{2}\]                 \[\le \frac{1}{\sqrt{2}}\] \[\Rightarrow \]               \[\left( 0,\,\,\frac{1}{\sqrt{2}} \right)\subset [0,\,\,\infty )\] So, function is not surjective but function is injective as for any \[0\le x\le \frac{x}{2},\,\,\sin \frac{x}{2}\] gives unique image.


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