JEE Main & Advanced Mathematics Applications of Derivatives Question Bank Increasing and Decreasing Function

  • question_answer
    Which one is the correct statement about the function \[f(x)=\sin 2x\]

    A)            \[f(x)\] is increasing in \[\left( 0,\frac{\pi }{2} \right)\] and decreasing in \[\left( \frac{\pi }{2},\pi  \right)\]

    B)            \[f(x)\] is decreasing in \[\left( 0,\frac{\pi }{2} \right)\] and increasing in \[\left( \frac{\pi }{2},\pi  \right)\]

    C)            \[f(x)\] is increasing in \[\left( 0,\frac{\pi }{4} \right)\] and decreasing in \[\left( \frac{\pi }{4},\frac{\pi }{2} \right)\]

    D)            The statements ,  and  are all correct

    Correct Answer: C

    Solution :

               As \[f(x)=\sin 2x\Rightarrow f'(x)=2\cos 2x\]            Obviously \[f'(x)>0\]in \[\left( 0,\frac{\pi }{4} \right)\] and \[f'(x)<0\]in \[\left( \frac{\pi }{4},\,\frac{\pi }{2} \right)\]                    Hence the result.


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