JEE Main & Advanced Sample Paper JEE Main Sample Paper-8

  • question_answer
    DIRECTION (Qs. 82): Each of these questions contains two statements: Statement-1 (Assertion) and Statement-2 (Reason). Choose the correct the answer (Only one option is correct) from the following- Consider \[I=\int\limits_{\pi /4}^{\pi /4}{\frac{dx}{1-\sin x}}\]
    Statement-1: \[1=0\] because
    Statement-2: \[\int\limits_{a}^{a}{f(x)dx=0.}\]wherever f (x) is an odd function.

    A)  Statement-1 is false, Statement-2 is true

    B)  Statement-1 is true, Statement-2 is true, and Statement-2 is a correct explanation for Statement-1

    C)  Statement-1 is true, Statement-2 is true; Statement-2 is not a correct explanation for Statement-1.

    D)  Statement-1 is true, Statement-2 is false.

    Correct Answer: A

    Solution :

     \[f(x)=\frac{1}{1-\sin x}\]and\[f(-x)=\frac{1}{1+\sin x}\] \[\therefore \]\[\int\limits_{-\pi /4}^{\pi /4}{\frac{dx}{1+\sin x}}\]                 Now, \[f(x)+f(-x)=2I\int\limits_{-\pi /4}^{\pi /4}{\frac{2dx}{1-{{\sin }^{2}}x}}\] \[\Rightarrow \]\[II\int\limits_{-\pi /4}^{\pi /4}{\frac{dx}{{{\cos }^{2}}x}}.\]This is an even function \[\therefore \]\[I=2\int\limits_{0}^{\pi /4}{{{\sec }^{2}}xdx\ne 0}\Rightarrow \]Statement-1 is false.


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