JEE Main & Advanced Mathematics Indefinite Integrals Question Bank Integration by Substitution

  • question_answer
    \[\int_{{}}^{{}}{\frac{\sin 2x}{\sin 5x\sin 3x}}\ dx=\]

    A)            \[\log \sin 3x-\log \sin 5x+c\]  

    B)            \[\frac{1}{3}\log \sin 3x+\frac{1}{5}\log \sin 5x+c\]

    C)            \[\frac{1}{3}\log \sin 3x-\frac{1}{5}\log \sin 5x+c\]

    D)            \[3\log \sin 3x-5\log \sin 5x+c\]

    Correct Answer: C

    Solution :

                       \[\int_{{}}^{{}}{\frac{\sin 2x}{\sin 5x\sin 3x}\,dx}=\int_{{}}^{{}}{\frac{\sin (5x-3x)}{\sin 5x\sin 3x}\,dx}\]                                   \[=\int_{{}}^{{}}{\frac{\sin 5x\cos 3x-\cos 5x\sin 3x}{\sin 5x\sin 3x}\,dx}\]                                                                 \[=\frac{1}{3}\log \sin 3x-\frac{1}{5}\log \sin 5x+c.\]


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