JEE Main & Advanced Mathematics Indefinite Integrals Question Bank Mock Test - Integrals

  • question_answer
      \[\int \frac{dx}{\cos x+\sqrt{3}\sin x}\] is equal to

    A) \[\frac{1}{2}\log \,\tan \left( \frac{x}{2}+\frac{\pi }{12} \right)+c\]

    B) \[\frac{1}{2}\log \,\,\tan \left( \frac{x}{2}-\frac{\pi }{12} \right)+c\]

    C) \[\log \,\,\tan \left( \frac{x}{2}+\frac{\pi }{12} \right)+c\]

    D) \[\log \,\tan \left( \frac{x}{2}-\frac{\pi }{12} \right)+c\]

    Correct Answer: A

    Solution :

    [a] \[\int{\frac{dx}{\cos +\sqrt{3}\sin x}=\frac{1}{2}\int{\frac{dx}{\frac{1}{2}\cos x+\frac{\sqrt{3}}{2}\sin x}}}\] \[=\frac{1}{2}\int{\frac{dx}{\cos \left( x-\frac{\pi }{3} \right)}}=\frac{1}{2}\int{\sec \left( x-\frac{\pi }{3} \right)dx}\] \[=\frac{1}{2}\log \tan \left( \frac{x}{2}-\frac{\pi }{6}+\frac{\pi }{4} \right)+c\] \[=\frac{1}{2}\log \tan \left( \frac{x}{2}+\frac{\pi }{12} \right)+c\]


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