JEE Main & Advanced Mathematics Trigonometric Identities Question Bank Trigonometrical ratios of sum and difference of two and three angles

  • question_answer
    If \[\tan A=2\tan B+\cot B,\]then \[2\tan (A-B)=\]

    A) \[\tan B\]

    B) \[2\tan B\]

    C) \[\cot B\]

    D) \[2\cot B\]

    Correct Answer: C

    Solution :

    \[2\,\,\tan \,(A-B)=2\,\left( \frac{\tan A-\tan B}{1+\tan A\tan B} \right)\] \[=2\frac{(2\tan B+\cot B-\tan B)}{1+(2\,\tan B+\cot B)\,\tan B}=2\,\frac{\tan B+\cot B}{2\,(1+{{\tan }^{2}}B)}\] \[=\frac{\cot B\,({{\tan }^{2}}B+1)}{(1+{{\tan }^{2}}B)}=\cot B\].


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