CET Karnataka Engineering CET - Karnataka Engineering Solved Paper-2006

  • question_answer
    The function \[f:X\to Y\] defined by \[f(x)=\sin x\] is one-one but not onto, if X and Y are respectively equal to :

    A)                  R and R

    B)  \[\left[ 0,\frac{\pi }{2} \right]\] and [0,1]

    C)  \[\left[ \frac{-\pi }{2},\frac{\pi }{2} \right]\] and [-1, 1]

    D)  \[\left[ \frac{-\pi }{2},\frac{\pi }{2} \right]\] and [-1, 1]

    Correct Answer: C

    Solution :

    Since \[f:X\to Y,\] then \[f(x)=\sin x\] Now, take option [c]. Domain \[=\left[ 0,\frac{\pi }{2} \right],\] Range \[=[-1,1]\] For every value of x, we get unique value of y. But the value of y in \[[-1,0)\] does not have any pre-image. \[\therefore \] Function is one-one but not onto.


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