2. Questions Bank
  3. JEE Main & Advanced
  4. Mathematics
  5. Applications of Derivatives

JEE Main & Advanced Mathematics Applications of Derivatives Question Bank Maxima and Minima

  • question_answer
    The minimum value of the function \[2\cos 2x-\cos 4x\]in \[0\le x\le \pi \]is

    A)            0

    B)            1

    C)            \[\frac{3}{2}\]

    D)            ? 3

    Correct Answer: D

    Solution :

               \[y=2\cos 2x-\cos 4x\]                      \[=2\cos 2x(1-\cos 2x)+1=4\cos 2x{{\sin }^{2}}x+1\]                    Obviously, \[{{\sin }^{2}}x\ge 0\]            Therefore to be least value of y, \[\cos 2x\]should be least i.e., \[-1\]. Hence least value of y is \[-\,4+1=-3\].


You need to login to perform this action.
You will be redirected in 3 sec spinner