JEE Main & Advanced Mathematics Functions Question Bank Functions

  • question_answer
    If \[f:R\to S\] defined by \[f(x)=\sin x-\sqrt{3}\cos x+1\]is onto, then the interval of S is [AIEEE 2004; IIT Screening 2004]

    A)                    [?1, 3]

    B)            [1, 1]

    C)            [0, 1]

    D)            [0, ?1]

    Correct Answer: A

    Solution :

                \[-\sqrt{1+{{(-\sqrt{3})}^{2}}}\le (\sin x-\sqrt{3}\cos x)\le \sqrt{1+{{(-\sqrt{3})}^{2}}}\]                    \[-2\le (\sin x-\sqrt{3}\cos x)\le 2\]                    \[-2+1\le (\sin x-\sqrt{3}\cos x+1)\le 2+1\]                    \[-1\le (\sin x-\sqrt{3}\cos x+1)\le 3\] i.e., range \[=[-1,\,\,3]\]                    \ For f to be onto \[S=[-1,\,\,3]\].


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