JEE Main & Advanced Mathematics Functions Question Bank Self Evaluation Test - Relation and Functions-II

  • question_answer
    If \[f:R\to S,\]defined by \[f(x)=sinx-\sqrt{3}\cos x+1,\] is onto, then the interval of S is

    A) \[[-1,3]\]

    B) \[[-1,1]\]

    C) \[[0,1]\] 

    D) \[[0,3]\]

    Correct Answer: A

    Solution :

    [d] \[f(x)\] is onto \[\therefore S=range\,of\,f(x)\] Now \[f(x)=\] \[\sin x-\sqrt{3}\cos x+1=2\sin \left( x-\frac{\pi }{3} \right)+1\] \[\because -1\le \sin \left( x-\frac{\pi }{3} \right)\le 1\] \[-1\le 2\sin \left( x-\frac{\pi }{3} \right)+1\le 3\] \[\therefore f(x)\in [-1,3]=S\]


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