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

  • question_answer
    The value of the definite integral,  \[\int\limits_{{{\theta }_{1}}}^{{{\theta }^{2}}}{\frac{d\theta }{1+\tan \theta }}=\frac{50\,1\pi }{K}\]were \[{{\theta }_{2}}=\frac{1003\pi }{2008}\]and \[{{\theta }_{1}}=\frac{\pi }{2008}.\]The value of K equals

    A)  2007                     

    B)  2006

    C)  2009                     

    D)  2008

    Correct Answer: D

    Solution :

     \[{{\theta }_{1}}+{{\theta }_{2}}=\frac{\pi }{2}\] \[\therefore \]\[I=\int\limits_{{{\theta }_{1}}}^{{{\theta }_{2}}}{\frac{d\theta }{1+\tan \left( \frac{\pi }{2}-\theta  \right)}}=\int\limits_{{{\theta }_{1}}}^{{{\theta }_{2}}}{\frac{\tan \theta d\theta }{1+\tan \theta }}\] And also\[I=\int_{\theta 1}^{\theta 2}{\frac{d\theta }{1+\sin \theta }}\] \[\therefore \]\[2I=\int\limits_{{{\theta }_{1}}}^{{{\theta }_{2}}}{d\theta ={{\theta }_{2}}-{{\theta }_{1}}=\frac{1002\pi }{2008}\Rightarrow I=\frac{50l\pi }{2008}}\] Hence, K= 2008.


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