JEE Main & Advanced Mathematics Trigonometric Identities Question Bank Trigonometrical ratios of multiple and sub multiple angles

  • question_answer
    If \[2\tan A=3\tan B,\]then \[\frac{\sin 2B}{5-\cos 2B}\]is equal to [AMU 2001]

    A) \[\tan A-\tan B\]

    B) \[\tan (A-B)\]

    C) \[\tan (A+B)\]

    D) \[\tan (A+2B)\]

    Correct Answer: B

    Solution :

    \[2\tan \Alpha =3\tan B\] Þ \[\tan A=\frac{3}{2}\tan B=\frac{3}{2}t\],  [Let \[\tan B=t\]] Þ \[\sin 2B=\frac{2t}{1+{{t}^{2}}},\cos 2B=\frac{1-{{t}^{2}}}{1+{{t}^{2}}}\] \ \[\frac{\left( \frac{2t}{1+{{t}^{2}}} \right)}{5-\left( \frac{1-{{t}^{2}}}{1+{{t}^{2}}} \right)}\]\[=\frac{2t}{4+6{{t}^{2}}}=\frac{t}{2+3{{t}^{2}}}=\tan (A-B)\].


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