Manipal Engineering Manipal Engineering Solved Paper-2012

  • question_answer
    Domain of definition of function\[f(x)=\sqrt{{{\sin }^{-1}}(2x)+\frac{\pi }{6}}\]for real-valued of\[x\], is

    A) \[\left[ -\frac{1}{4},\,\,\frac{1}{2} \right]\]                          

    B) \[\left[ -\frac{1}{2},\,\,\frac{1}{2} \right]\]

    C) \[\left[ -\frac{1}{2},\,\,\frac{1}{9} \right]\]          

    D)        \[[0,\,\,\pi ]\]

    Correct Answer: A

    Solution :

    Here,\[f(x)=\sqrt{{{\sin }^{-1}}(2x)+\frac{\pi }{6}}\], to find domain, we must have, \[{{\sin }^{-1}}(2x)+\frac{\pi }{6}\ge 0\]  \[\left( but\,\,-\frac{\pi }{2}\le {{\sin }^{-1}}\theta \le \frac{\pi }{2} \right)\] \[\therefore \]  \[-\frac{\pi }{6}\le {{\sin }^{-1}}(2x)\le \sin \frac{\pi }{2}\] \[\Rightarrow \]               \[\sin \left( -\frac{\pi }{6} \right)\le 2x\le \sin \left( \frac{\pi }{2} \right)\] \[\Rightarrow \]               \[-\frac{1}{2}\le 2x\le 1\] \[\Rightarrow \]               \[-\frac{1}{4}\le x\le \frac{1}{2}\] \[\Rightarrow \]               \[x\in \left[ -\frac{1}{4},\,\,\frac{1}{2} \right]\]


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