Manipal Engineering Manipal Engineering Solved Paper-2008

  • question_answer
    The maximum value of\[\sin \left( x+\frac{\pi }{6} \right)+\cos \left( x+\frac{\pi }{6} \right)\]in the interval \[\left( 0,\,\frac{\pi }{2} \right)\] is attained at

    A) \[x=\frac{\pi }{12}\]                       

    B) \[x=\frac{\pi }{6}\]

    C) \[x=\frac{\pi }{3}\]         

    D)        \[x=\frac{\pi }{2}\]

    Correct Answer: A

    Solution :

    Now,\[\cos \left( x+\frac{\pi }{6} \right)+\sin \left( x+\frac{\pi }{6} \right)\] \[=\sqrt{2}\left[ \frac{1}{\sqrt{2}}\cos \left( x+\frac{\pi }{6} \right)+\frac{1}{\sqrt{2}}\sin \left( x+\frac{\pi }{6} \right) \right]\] \[=\sqrt{2}\cos \left( x+\frac{\pi }{6}-\frac{\pi }{4} \right)\] \[=\sqrt{2}\cos \left( x-\frac{\pi }{12} \right)\] For maximum value \[x=\frac{\pi }{12}\]


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